Scan every package registered by Spring framework, instead of the whole class-path

[fabiocarvalho777]

The scanning registration method scans the whole classpath when looking for JAX-RS Application sub-class, and that impacts greatly performance during application start-up.

Instead of that, only packages registered to be scanned by Spring framework should be searched when registering JAX-RS Application sub-classes (regardless of them being Spring beans or not).

[fabiocarvalho777]

Here is a temporary, but functional and complete, solution for this issue (under branch issue_69).

This issue can be implemented only when working on version 3.0.0 though, which should happen when Spring Boot 2.0.0 or RESTEasy 4.0.0 is released.