Adding new "consent unavailable" condition

- restricting use of "consent unavailable" and "unreachable" to administrators and curators only
- modifying participant status report (now shows all conditions)
Adding fix to modifier's get_where_columns(), get_group_columns() and get_order_columns() methods
Giving supervisors access to the 'unreachable' condition
Adding database\participant::get_release_date() method
Fixing bug (wrong service record) in participant report
Improving performance of participant report
Adding a new participant_status pull operation
Sorting participant status output
Adding "No Site" as an option to the site parameter

This new option will match all participants who have no site (due to
being outside of the jurisdiction or site/region selection).

Also, a bug which caused an error when trying to match participants
based on events has been fixed.
Fixing bug in participant report caused by last update
More fixes to participant report
Fixing bug in participant report
Merge remote branch 'origin/release' into develop