Allow relationships to be conditionally emitted in REST resource representations

From : http://lists.jboss.org/pipermail/forge-dev/2013-October/003484.html

When you have too many @OneToMany or @ManyToMany relationships, you end up
with several queries that JOIN FETCH several/different relationships. So
what I usually do when things are complex is :

findAll
findAllWithRelations (meaning all relations are FETCH)

or more specific (when things are really really complex)

findAllWithBooks
findAllWithAuthors
findAllWithBooksAndAuthors