A lot of new functions

Functions:
+dropItem
+setSpawn
+destroyBlock
+setTime
+getTime
+setGameType (requires world reload however)
+getGameType
+setOnFire
+bl_delData
Callbacks:
+blockDestroy
Features:
+After removing script, data saved by it is also removed
Added ModPE.selectLevel method for loading more worlds; removed a few bl_-prefixes; fixed the error concerning invalid prototype on a header
Merge remote-tracking branch 'mrarm/master'

Conflicts:
	src/net/zhuoweizhang/mcpelauncher/ScriptManager.java