Refactor open dialog with separate open preferences for videos, channels and playlists

[Stypox]

RouterActivity is currently rather crappy, since the code is difficult to read and edit and not well structured. Therefore it needs some attention. The open dialog needs to be improved so that it is more consistent (see #4259 (comment) ). We should also handle in a better way things that are not videos, i.e. channels and playlists, and videos with only audio (SoundCloud). We should allow the user to choose different open actions for videos, playlists and channels, since after #4259 the user may want to e.g. always autoplay videos and always show playlist info.

[SameenAhnaf]

Maybe, another preference for Shared Video from Playlist should be added too. Morr details: #7643