Merge pull request #194 from acstache/bleeding

Keep track of which players picked which class

- Change MutableInt counters to String sets of player names
- Add getPlayersWithClass() method
Fix default fixed waves.
Some 1.6 updates...
Merge branch 'bleeding' of github.com:garbagemule/MobArena into bleeding
Use item number for hay bales until 1.6
Leave out 1.6 stuff until a stable release.
Update plugin.yml towards next release.