DB replacement for cached prefix trees

+ Adds a DAO for filling in and querying over principal-related strings.
+ Renames OriginClient to DomainType so that it can appear in the javadocs (web client pom update required)
+ Adds triggers for change message (type PRINCIPAL) in the UserGroup and UserProfile DAOs
+ Adds a worker that fills in the new prefix lookup table based on the PRINCIPAL and TEAM messages.  

(Sort of) needs changes to be introduced by #932