Support set and display user ratings

[wutschel]

Motivation

Currently the app only displays "rating", which usually is a IMDB rating for movies, TV Shows or episodes (1-10 rating) and related to metadata tags for music files (1-5 rating). Kodi also supports "user rating" (1-10 rating) which can be read and also set via JSON API. It will be good to add the support for setting and displaying "user rating".

Rating vs. user rating

Following Kodi UI I would go for the same approach to either show "rating" or "user rating", which can be configured in the App's settings. This way conflicts with different rating system would be avoided.

Setting user rating

Setting a rating would only be supported for the user rating to avoid messing around too much with the data coming from scrapers. I would place a new option "User Rating" to the action menu when long pressing an item. I am also thinking of adding a rating button to the NowPlaying screen -- even though this might become a bit loaded.

Constraints

Setting / changing the rating will most likely require to resynchronize the data again.

[wutschel]

Layout

This also requires layout changes for the list view. Currently the rating is displayed in 3rd row, which is not even visible for songs, albums or episodes. This could be changed towards always having the rating right aligned in top row, which would in effect shorten the item's label.

[wutschel]

First draft and quick impression how this could like like: https://ibb.co/67x7SxWQ