CopyOnWriteArrayList, to allow listeners to unregister themselves due to
an event while preventing ConcurrentModificationExceptions.
Modified all GameDataElement.elementChanged concrete implementation to
remove the backlink from the oldOne.An element pointed by an altered
element will not show the game source element in its backlink list
anymore.
Added support for the new "colorfilter" map property. Due to Java2D
having no correct color filter support, only the "blackXX" values can be
previwed. "bw" and "invert" cannot, the performance cost was simply way
too high.
