Move more logic into INIT block
Automatically switch to autocompleter on too many Owners

This avoids the server- and client-side slowdown associated with
generating and rendering overly large drop-downs.  The most common cause
of this is granting OwnTicket to the Everyone group.
Only display privileged users in Owner drop-downs

Configurations in which unprivileged users are expected to own tickets
are vanishingly small or non-existant; however, it is a common
misconfiguration to grant Everyone the OwnTicket right.

Limit entries in the Owner dropdown to only privileged users.
Configurations which require unprivileged users be able to own tickets
may use the autocompleter.
update docs for AutocompleteOwners in the config
Merge branch '4.2/owner-display'

Conflicts:
	docs/UPGRADING-4.2
	share/html/Elements/SelectOwnerDropdown