List items that are missing from Peertube API that could be useful to OwnTube client

[mblomdahl]

I added some issues based on or conversation this morning, please check them out and see if there's anything that you'd like to comment on (and add more as you see fit).

Updates on the PeerTube server side:

• Update PeerTube API for video-playlists to include/exclude local Playlists .github#9
• Update PeerTube API for video-playlists to exclude empty Playlists .github#10
• Update PeerTube API for video-channels to include/exclude local Channels .github#11
• Update PeerTube API for video-channels to exclude empty Channels .github#12
• Update PeerTube API for videos to filter on categoryOneOf=null for Uncategorized .github#14

The idea of adding a backend service on our end as a optional "accelerator" (enabled by passing ?backend=videos.com&boost=yes to the web client, for example):

• Create a backend service for accelerating Channel discovery responsiveness .github#13
• Create a backend service for filtering out Uncategorized videos .github#15