HV-877 Discovering and registering type use constraints

A bit smaller. This PR focuses on discovering and registering type use constraints for the base use cases. 

Cascaded type usage, and the actual validation of the constraints will be in separate PRs to make things easier to track.

Note: you'll need Java 8u20 for this to work. There is a bug with parameters annotated types with earlier JDKs.
Should this be named `findTypeParameterConstraints()`? AFAICS, "type use" would be more something like "private List<@Email String> mails".