Fixed a huge delete {WPS, Process} bug!
* AbstractQosEntity and MeasuredDataEntity-objects was not removed if a wps or a wps process was deleted (ends up in an exception)
* Every Entity now has a delete named query!
* DataAccess now implements a delete cascade behavior because of bad delete statement support of JPA: "However, delete queries do not honor cascade rules: no entities other than the type referenced in the query and its subclasses will be removed" (http://wiki.eclipse.org/EclipseLink/UserGuide/JPA/Basic_JPA_Development/Querying/JPQL#Delete_Queries)