more flexible user-settings

[xDashh]

I think right now for each (new) user setting the backend database has to be modified. It would be nice if we just stored a json blob(?) in the db, and people could modify that easily / new settings could be added without too much trouble.

Related issues/feature-requests:

• hide streams that fit some criteria nsfw stream preview hiding #18 add a way to hide offline streams #39
• possible misc. UI modifications add theater mode #83
• being able to remove warning pages like for advanced and nsfw ( add nsfw warning when opening streams #97 ) permanently