FindBugs warning cleanup

Fix possible null dereference in AbstractShape.equals()
Replaced manual array copy in MathOp
Replaced string-concatenation-in-loop for StringBuilder use
Replaced EAdShape clone() with copyShape() returning EAdShape
Removed some equals() from model, left most hashCode()s alone
General code cleanup in ResourceCreator

Now auto-called with ant task during build
Also cleaned poms a bit: exec plugin version dependency is now in root
Removed Messages.java (also regenerated on recompile)
Fixed all warnings (many with the help of suppresswarnings(unchecked))