Improve constraints implementation
Merge
Merge branch 'master' of
https://github.com/genericsystem/genericsystem2011.git

Conflicts:
	genericsystem-impl/src/main/java/org/genericsystem/core/CacheImpl.java
	genericsystem-impl/src/main/java/org/genericsystem/systemproperties/constraints/AbstractAxedConstraintImpl.java