Save volume state, more playlist tools, etc.

Cleaner playlist look (with glow!). Recursive add and playlist sort not implemented
yet. Recursive will likely require C++ side implementation (FolderListModel's both
asynchronous and highly limited), while sorting will just take a bit of JS. Also,
still needs uniqueness enforced. Finally, drag re-ordering and drag/flick to
add/remove are later toys to add.