Moved GUI classes to org.jtrfp.trcl.gui package.
Added instance vars to supply strong references for DEFObjects and
PUPObjects keeping safe from GC.
Add PropertyChangeListener support to TR.*game.
Add support for Game abort and level skip.
ThreadManager gameplay pause now blocks until paused/unpaused.
SpacePartitioningGrid now uses weak references for branch grids.
Misc cleanup and refactorings.
Added weak referencing to IndirectProperty target to avoid memleak.