4.51v Message remove

1. Now you can remove selected message completely.
2. Preparation for further works on custom online periods per department.
3. Online/Offline peridios for operator will be tracked more precisely.
4. Switch from || to OR syntax for SQL queries.
5. Hours format for work hours switched to 23:59 as max value for end period.

execute doc/update_db/update_321.sql for update

What's Changed

Full Changelog: 4.50v...4.51v