Add remove button to data model preference pages
Merge branch 'PredicateDev' of https://github.com/aradouan/ReqCycle

Conflicts:
	plugins/org.eclipse.reqcycle.repository.data.ui/src/org/eclipse/reqcycle/repository/data/ui/preference/pages/DataModelsPreferencePage.java
	plugins/org.eclipse.reqcycle.repository.data.ui/src/org/eclipse/reqcycle/repository/data/ui/preference/pages/ScopesPreferencePage.java