Added more predefined user/profiles

_query - used by the query subsystem
_index - used by the indexing subsystem
_xdcr - used by XDCR

Change-Id: I6e00518ebc03ed3f7cf1efe5fe0a1270be5d6b97
Reviewed-on: http://review.couchbase.org/43147
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Dave Rigby <daver@couchbase.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>