TRUNK-4485: Modifying provider search to make it configurable

This tickets aims to make search mode for providers when using identifier configurable through the global property. Instead of suing MatchMode.ANYWHERE, the code is modified to allow only EXACT and START.
Wait, why are we defining string constants that duplicate the enum values at https://docs.jboss.org/hibernate/orm/3.2/api/org/hibernate/criterion/MatchMode.html ?

Your code should just be doing try { MatchMode.valueOf(gpValue) } catch ...