macosx: Redesign the selected group album table view

This PR changes the design of the album-based group selection table view. The new design makes better use of vertical space and is more visually appealing.

This screenshot shows the changes in this PR, plus !2317 (merged) and !2314 (merged)

Current master:

Signed-off-by: Claudio Cambra claudio.cambra@gmail.com