view: update selection patterns and clean views a little bit

Version 2 - July 2

Solved issues

• search view:
  • Right click on a search results focuses it, unfocusing the search entry.
  • Activating favorite song in selection mode also activates selection.
• Artist view:
  • Left padding in selection mode seems off (selection box to close to window border).

Remaining issues

• search view:
  • Vertical shift on entering selection mode.
• Artist view
  • Selecting first item (Artist) is impossible, selecting 2nd also selects first (likely some off-by-1 error).

Version 3 - July 3

• new: Correctly style sidebars (see #37 (closed))