JBIDE-17296 - Missing warning decorator on the "JAX-RS Web Services" node when no application is defined

"JAX-RS Web Services" node in project explorer shows a "warning" decorator (by default)
if no application was defined, unless no JAX-RS element exists in the project.
JBIDE-16981 - Validation of @Path parameters binding ignores @PathParam fields
JBIDE-17276 - JAX-RS Endpoints should not display an error marker when error is on JAX-RS Application

Error marker is only shown on the "JAX-RS Web Services" node in the Project Explorer, not on all Endpoint child nodes.
JBIDE-17177 - Wrong @NameBinding quick fix for a @Target annotation

Fixing the quick fix applied
Refactoring the code for quickfixes
Including Java Proposals when missing values (with or without parenthesis)
Adding JUnit tests to check the quckfixes proposals and their application
Also adding a content assist proposal for the @HttpMethod annotation value, based on the annotation name.

Also fixed JBIDE-17307 Missing label and broken link for JAX-RS problem severity configuration
JBIDE-17151 - Improve the Restful Services Wizard
JBIDE-15526 - JAX-RS validation problems are not linked

Fixed by keeping info about removed elements in the metamodel
until the validation runs.
Added and fixed some JUnit tests to verify.
JBIDE-16483 - Updating minimum execution environment to 1.6