[WIP] Music command rework

[OmniTroid]

Move all state and commands related to music to separate class

Proposed command renames:

/currentmusic -> /music showcurrent
/getmusic -> /music playlast
/jukebox_toggle -> /music mode (vote, queue, shuffle, normal)
/jukebox_skip -> /music skip
/jukebox -> /music info (show info about queue/votes) (maybe merge /music current into this one)
/play -> /music play
/play_once -> /music playonce (may be more sensible to have a setting to turn looping on and off)
/blockdj -> /music block
/unblockdj -> /music unblock
/musiclists -> /music showlists
/musiclist -> /music loadlist
/area_musiclist -> /music loadarealist
/hub_musiclist -> /music loadhublist
/random_music -> /music playrandom
/musiclist_save -> /music savelist
/musiclist_rebuild -> /music rebuildlist
/musiclist_remove -> /music removelist
/musiclist_add -> /music addlist

old commands can easily be aliased to new ones to keep them working if that's required

I see that client_manager has a lot of functions and state related to music too, but let's not dive into that right now.

[OmniTroid]

Not really happy how this turned out. The concept is there, but the fact that this set of commands don't follow existing conventions (eg. decorators as permission) breaks internal consistency. It may have sense to have a MusicManager for each area to handle the current state and state changes (queuing, etc) as well as the music stuff which is in client currently (some parsing of musiclists and whatnot), but the commands there don't seem quite right. Anyways, it's a concept for reorganizing music commands, which may or may not be realized.