Fix naming and unused parameter issues.
Move ValidationUtil to ch.acanda.eclipse.pmd.ui.model

This fixes an API issue with a parameter of one of the utility methods.
Add missing dependencies which prevented some rules from beeing executed

The dependencies for Saxon and Saxon DOM were missing which lead to a
ClassNotFoundException when the Java rules OneDeclarationPerLine or
AvoidLiteralsInIfCondition were executed.

This fixes #17.