thumbnails in LBRY

[lyoshenka]

the goal is to store claim thumbnails within the LBRY network

changes

• every command that takes thumbnail_url also takes thumbnail_path, a path on the local filesystem to the thumbnail image
• if given, the sdk turns that file into a stream and puts the sd hash into the thumbnail Source. it also makes the file available on the DHT

there might be some complexity in the file manager or stream manager because we used to have the assumption that one claim = one stream. but with this, one claim might have two streams (the stream itself and the thumbnail)

open questions

• there's no way to store image dimensions. is that ok?
• what filetypes are acceptable for thumbnails?
• how to return thumbnail data back to the app?
• will displaying a list of claims be slow because you have to download all the thumbnails?