Library improvements

[OxygenCobalt]

This is related to multiple issues:

1. Disjointed Library UI: Songs on one tab but artists on another, can't set defaults [Related: Allow songs tab to be opened by default #12]
2. Can only see one item type at a time in the library view
3. No sorting on the songs view [Related: Sort Option in Songs Tab #16]
4. Sorting options are basic [No artist/album sorting]

Currently, the plans to fix these are:
1 and 2: Redesigned library UI with all items shown. A setting would be added that would allow this view to be customized. This is reliant on #36 however.
3 and 4: A sorting update that would add this to the songs view alongside some other options. Sorting by year would likely not be added here, as the current fast scroller could not accommodate it [and I don't want to change out the fast scroller unless there is sufficient demand].

This issue is the basis for a massive UI overhaul that will occur in the future, however details of that are still being worked out.

[OxygenCobalt]

Most of this has been completed save some odds-and-ends [Like view customization]. Closing this issue.