Major update for metadata and stats.
Statistics are saved in metadata entries, so I do not have to fallback to (rather complex) Scala constructs such as the Stackable trait pattern (which is not compatible with Java anyways).
A new property class is included with which i seek to minimize get/set clutter and a bit more clarity in terms of instance variables.
The metadata classes have been redesigned; easier-managable inheritance tree for the metadata system.
Merge remote-tracking branch 'origin/master'

Conflicts:
	src/world/TileLike.scala