prepare to support restful searches for queues, users and groups
restful search support for queues/users/groups
merge restful ticket search to dhandler to avoid replicated code
clean some replicated code
shouldn't allow user to search password field
allow restful user search only if current user has AdminUsers right

user data is sensible and shouldn't be seen easily.
besides, we don't have SeeUser right either.
search user defined groups only
whitelist of restful search fields

this is better than only blacklisting hardcoded "password"
allow < and > ops too
REST: show Disabled column for queues/groups
REST: handle Disabled column search for queues/groups/users
tests for restful search of queue/group/user
Merge branch '4.2/rest-search-refactor' into 4.2-trunk