Rename "length" key for music.yaml parsing

[NikoofDeath]

Currently, both aoprotocol and tsuserver refer to the parameter used to determine looping as "length" (and looks for "length" in music.yaml)

tsuserver3/server/network/aoprotocol.py

Line 729 in fefe5b0

name, length = self.server.get_song_data(self.server.music_list, args[0])

tsuserver3/server/tsuserver.py

Line 349 in fefe5b0

return song['name'], song['length']

However, once the song reaches play_music, the parameter becomes "loop", and then becomes "looping" in courtroom on the client, and again becomes "loop" in aomusicplayer

tsuserver3/server/area_manager.py

Line 313 in fefe5b0

def play_music(self, name, cid, loop=0, showname="", effects=0):

I understand looking for "length" in music.yaml, to keep compatibility with old music.yaml files that used that to indicated looping, but I believe it should look for a "loop" parameter first (and that should be the encouraged choice going forward), and be referred to as such in the code, to prevent confusion. (This also goes for making the naming in courtroom.cpp and aomusicplayer.cpp consistent for the client code).

[Crystalwarrior]

👍, I wanted to do this but kind of ran out of time due to deadlines.
Length will still be supported but the intended parameter will become loop