Add preroll video support

[1hitsong]

Changes
Added functionality to check if preroll videos are enabled and available. If so, they will play before any video, matching the functionality of the web client.

Issues
Fixes #448 #448

[neilsb]

On the server, while pre-rolls need to be enabled at the server level via the Plug-in, each user has an option whether to play them or not via the User Settings -> Playback -> Cinema Mode option. We should probably do similar on this client to prevent pre-rolls being forced on the user by a server admin. We can either use the web "Cinema Mode" option, or add our own User Setting to give similar control on the Roku.

When selecting a partially watched item, the Preroll plays before giving the user the popup menu of Continue / Restart. Would probably be better to show this menu first (Especially now there are options to mark watched, go to season, go to episode etc).

On web, if you're select a partially watched item them the preroll doesn't play at all. Might be worth implementing that too?

[1hitsong]

add our own User Setting to give similar control on the Roku.

I love this idea! Let's go this route.

When selecting a partially watched item, the Preroll plays before giving the user the popup menu of Continue / Restart. Would probably be better to show this menu first (Especially now there are options to mark watched, go to season, go to episode etc).

On web, if you're select a partially watched item them the preroll doesn't play at all. Might be worth implementing that too?

100%! I'll work on this as well.

[1hitsong]

@neilsb Updates made

[neilsb]

Looks like it almost perfects now. The last thing that I just noticed is that when Automatically play next episode is selected, the preroll plays between every episode. I'd suggest it's only wanted at the start of the first episode?

[1hitsong]

@neilsb Setting content updated. Added code to prevent intros before auto-played next episodes.

[neilsb]

All looks good.