Allow subclasses to override method of retrieving Concept in HibernateLogicObsDAO

This is related to bug TRAC-1876.

As a non-intrusive first step to fix the above bug, the attached patch abstracts the logic for retrieving the matching concept for a token name into it's own method. This will allow modules to subclass this DAO (and re-use the all of it's complex logic for handing Critieria), but override this particular behavior.

Win - I'll commit this to 1.5.x, but I assume it should not go to trunk, but instead into the logic module, correct? Can you do this?