Adds the database table structure for collaboration support
Add collaborator class
Parse collaborators from email header.
Unify user util routines
Add user lookup for ticket.
Add collaborator(s) utils to ticket class
Change TO address to a dropdown selection in anticipation of multi-email
support
Add CC section
Add collaborator management popup and ajax support
CSS fixup for dialog popup
Add ticket activity notice template
Cascade email and template lookup.
Reactor how template group and email are fetched.
Make variable %{recipient} a complex variable of type person.
Notify active collaborators on message/reply
Use close icon for dialog window close
Add message info bar
Merge branch 'feature/user_lookup-revisited' into feature/cc

Conflicts:
	include/ajax.forms.php
	include/ajax.tickets.php
	include/class.user.php
	include/staff/ticket-view.inc.php
help: Fixup wording on password expiration policy
tips: Auto-flip help tip pop-over