[dplay] Add support for playlists

[MrDemocracy]

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• You will be asked some questions and requested to provide some information, please read them carefully and answer honestly
• Put an x into all the boxes [ ] relevant to your issue (like this: [x])
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Make sure you are using the latest version: run youtube-dl --version and ensure your version is 2017.12.10. If it's not, read this FAQ entry and update. Issues with outdated version will be rejected.

• I've verified and I assure that I'm running youtube-dl 2017.12.10

Before submitting an issue make sure you have:

• At least skimmed through the README, most notably the FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones

What is the purpose of your issue?

• Bug report (encountered problems with youtube-dl)
• Site support request (request for adding support for a new site)
• Feature request (request for a new functionality)
• Question
• Other

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The following sections concretize particular purposed issues, you can erase any section (the contents between triple ---) not applicable to your issue

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If the purpose of this issue is a bug report, site support request or you are not completely sure provide the full verbose output as follows:

Add the -v flag to your command line you run youtube-dl with (youtube-dl -v <your command line>), copy the whole output and insert it here. It should look similar to one below (replace it with your log inserted between triple ```):

youtube-dl http://www.dplay.no/praktisk-info-med-jon-almaas/ -v
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'http://www.dplay.no/praktisk-info-med-jon-almaas/', u'-v']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2017.12.10
[debug] Python version 2.7.13 - Darwin-17.2.0-x86_64-i386-64bit
[debug] exe versions: ffmpeg 3.3.4, ffprobe 3.3.4, rtmpdump 2.4
[debug] Proxy map: {}
[generic] praktisk-info-med-jon-almaas: Requesting header
WARNING: Could not send HEAD request to http://www.dplay.no/praktisk-info-med-jon-almaas/: HTTP Error 405: Method Not Allowed
[generic] praktisk-info-med-jon-almaas: Downloading webpage
WARNING: Falling back on generic information extractor.
[generic] praktisk-info-med-jon-almaas: Extracting information
ERROR: Unsupported URL: http://www.dplay.no/praktisk-info-med-jon-almaas/
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/youtube_dl/extractor/generic.py", line 2163, in _real_extract
    doc = compat_etree_fromstring(webpage.encode('utf-8'))
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/youtube_dl/compat.py", line 2539, in compat_etree_fromstring
    doc = _XML(text, parser=etree.XMLParser(target=_TreeBuilder(element_factory=_element_factory)))
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/youtube_dl/compat.py", line 2528, in _XML
    parser.feed(text)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 1653, in feed
    self._raiseerror(v)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 1517, in _raiseerror
    raise err
ParseError: syntax error: line 1, column 0
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/youtube_dl/YoutubeDL.py", line 784, in extract_info
    ie_result = ie.extract(url)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/youtube_dl/extractor/common.py", line 437, in extract
    ie_result = self._real_extract(url)
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/youtube_dl/extractor/generic.py", line 3063, in _real_extract
    raise UnsupportedError(url)
UnsupportedError: Unsupported URL: http://www.dplay.no/praktisk-info-med-jon-almaas/

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If the purpose of this issue is a site support request please provide all kinds of example URLs support for which should be included (replace following example URLs by yours):

• Single video: http://www.dplay.no/praktisk-info-med-jon-almaas/season-1-episode-1/
• Single video: http://www.dplay.no/neste-sommer/season-1-episode-1-gratis/
• Playlist: http://www.dplay.no/praktisk-info-med-jon-almaas/
• Playlist: http://www.dplay.no/neste-sommer/

Note that youtube-dl does not support sites dedicated to copyright infringement. In order for site support request to be accepted all provided example URLs should not violate any copyrights.

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Description of your issue, suggested solution and other information

All the episode links can be found in a json file, that is loaded when the page loads.
Example with "Praktisk info med Jon Almaas": http://www.dplay.no/api/v2/ajax/shows/15882/seasons/?items=14&sort=episode_number_desc&video_types=-clip&page=0

[dirkf]

I believe these sites are now obsolete. Please comment in PR #32235 with current valid URLs for Scandinavian Discovery sites that ought to be supported.

[craftpag]

Hello MrDemocracy!

since you have mentioned:
Single video: http://www.dplay.no/praktisk-info-med-jon-almaas/season-1-episode-1/
Single video: http://www.dplay.no/neste-sommer/season-1-episode-1-gratis/
Playlist: http://www.dplay.no/praktisk-info-med-jon-almaas/
Playlist: http://www.dplay.no/neste-sommer/

A while ago, do you have a new solution to download neste sommer and praktisk info med jon almaas from discoveryplus.com/no with youtube-dl?
Hope you can help with a solution:)