AS-6665 Updating to HV 5

As discussed with @scottmarlow, here is the PR for updating to Hibernate Validator 5.x. The change comprises:

* Updated the HV dependency and adding ClassMate as dependency
* Removed any usages of removed, deprecated or HV-internal APIs
* Made `LazyValidatorFactory` working with other BV providers than HV if existent (with HV being the default)