VertexQuery based search for users who know users; use one method with Direction to control whether to find users who know userID or users userID knows.
rename exceptions under this format:

ProxStorGraph*  are exceptions thrown by ProxStorGraph and are meant to be consumed by Dao*
all other exceptions are thrown by the Dao* layers and are consumed by other Dao* and *Resource
drop reverse variant of getUserKnows*()
numerous com.giannoules.proxstor.user cleanup, exceptions, api updatae
exception name cleanup