implement checker
Merge
Merge branch 'dev' of https://github.com/genericsystem/genericsystem2014.git into dev
Refactoring
Refactoring
improve visibilities
Improve visibilities
Refactoring
Merge remote-tracking branch 'origin/dev' into erik

Conflicts:
	gs-kernel/src/main/java/org/genericsystem/kernel/AbstractVertex.java