implements changes following Flo's review

org.fortiss.tooling.kernel/trunk/model/kernel.ecore

org.fortiss.tooling.kernel/trunk/model/kernel.genmodel

org.fortiss.tooling.kernel/trunk/plugin.xml

...rtiss.tooling.kernel/trunk/schema/constraintVerifier.exsd

...src/org/fortiss/tooling/kernel/extension/IConstraint.java

...ortiss/tooling/kernel/extension/base/ConstraintBases.java

...rg/fortiss/tooling/kernel/internal/ConstraintService.java

...ortiss/tooling/kernel/internal/ToolingKernelInternal.java

...onstraintVerificationServiceIntrospectionDetailsItem.java

...rg/fortiss/tooling/kernel/service/IConstraintService.java

...rc/org/fortiss/tooling/kernel/utils/ConstraintsUtils.java