Return printed values as well when using --json flag

[FunnyPocketBook]

Closes #95

The change from game_ids=None to game_ids=[] is because None breaks the GraphQL query. If channel_videos_generator is being called without explicitly setting the named argument game_ids, None is being set, which is not compatible with the GraphQL query.

[nftchance]

Please merge this. There is elementary stack functionality missing from this repository for it to actually be helpful.

[ihabunek]

@FunnyPocketBook I've merged the second commit. I commented on #95 regarding the other one.