Allow DryRun => 1 to CreateTicket, which returns the txn

This can hence he used to implement PreviewScrips, at the cost of losing some ticket numbers.
Allow explicit addresses to skip, in addition the SkipNotification sets

RTIR uses the SkipNotification argument to Create (added in 7e0e0a5) to
squelch whole classes of users at create time.  2047c32 added a
TransSquelchTo argument to RT::Ticket->Create to implement this
create-time squelching, but didn't allow explicit control of individual
addresses at the level of the CreateTicket API.

Add the same TransSquelchTo argument to RT::Interface::Email's
CreateTicket, which allows an explicit additional set of addresses to
squelch, in addition to those that SkipNotification adds.
Merge branch '4.2/dry-run-ticket-create'