Use the searchable profile fields from the internal artefact instead
of the 'public' fields.  Because these are all fields from the usr table,
this the join on the artefact table to be removed, and the same query can
then be used for both postgres and mysql.

Use either = or ILIKE to match fields depending on the value of the
'exactusersearch' config option.  Use of = allows the lowercase index to
be used in postgres searches.

Change the query to AND the search terms together instead of using OR.

Change-Id: I3a409149ee413fe59060e4e507ce58e34ebeb115
Signed-off-by: Richard Mansfield <richard.mansfield@catalyst.net.nz>