FORGE-867 Save JPA entities only on modifications.

This change is done to prevent the Faces scaffold from modifying JPA entities in TicketMonster. None of the JPA entities in TicketMonster need modification to accomodate the generated scaffold, and hence the source formatting should not be lost.

A dirty bit is used to track whether the JPA entity is modified or not, and the entity is saved only if modified by the scaffold.