Begins SimpleDesk general processing.
Several things are done here, the results of which are unilaterally assumed by all other SimpleDesk functions.
- work out which departments are applicable, and which department we are currently in (as far as possible)
- set up general navigation
- see if the URL or POST data contains a ticket, if so sanitise and store that value
- see if a msg was specified in the URL, if so identify the relevant ticket
- add in the helpdesk CSS file
- identify the sub action to direct them to, then send them on their way.