HV-837

Hi @hferentschik, I'm still going to add some more tests, but some feedback is already welcome :)

With this change, the general approach for the PE is this:

* If there already is a bean for `Validator` don't register one; the same for `ValidatorFactory`; So it's assumed whatever component has registered these beans, has taken care of the correct qualifiers etc.
* Otherwise two beans are registered representing the default validator and validator factory as per the BV definition (i.e. based on `META-INF/validation.xml`, also taking the default provider into account); If HV is the default provider, these beans will have the `HibernateValidator` qualifier as well
* If HV is _not_ the default provider, these beans will not have the `HibernateValidator` and another pair of beans is registered, this time *with* the qualifier and explicitly using HV as provider

WDYT?