Fixed negative Timers

caused by NoClassDefFound for
mc.alk.tracker.objects.WLT;

Fixed an issue where BombArena would break when BattleTracker was not
installed on the server (making it a mandatory dependency).

changed:
DetonationTimer.java
DefuseTimer.java
PlayerStats.java
pom.xml (version 1.1.2)

BattleTracker should now be an optional dependency again.