JBIDE-15402 - Doubled warnings Multiple JAX-RS Activators

Removed the duplicate validation at both the JaxrsApplications level and kept the one
at the JaxrsMetamodel level.
JBIDE-12860 - JAX-RS validation problems are not linked

Added a custom JAXRS_PROBLEM_TYPE attribute in JAX-RS markers.
Those JAX-RS Problem markers are now indexed with Lucene.
Thus, it becomes possible to look for resource that have the same
error as a given resource, even if this later one has been deleted.
(eg: looking for duplicate application problem after an application
has been removed).
When a JAX-RS Element is removed, its associated JAX-RS Markers are
removed from the index *during the validation phase* (the markers
still exist and are still indexed until the validation is performed).
Added some JUnit tests to verify the good behaviour againts the case
where a project has 2 JAX-RS application then one is removed.