Update NamePrefix regex to match CF grouping when provided

8d87f2ce added a grouping string to the NamePrefix. Update
the autocomplete helper to handle it. Use
_ParseObjectCustomFieldArgs to avoid duplicating the regex.
Update autocomplete calls to include object type

The previous autocomplete queries were successful with the old
autocomplete cf regex, but object type (i.e., RT::Ticket) is
correctly required in the CF arg string by the regex in
_ParseObjectCustomFieldArgs.
Merge branch '4.2/cf-autocomplete-grouping-name' into 4.2-trunk