Create RT::IR::Test::GnuPG

This gives us a shim similar to RT::Test::GnuPG to do all the config
writing and ensure that GnuPG is turned on.  This cargo cults frmo
RT::Test::GnuPG *except* that it calls add_rights rather than set_rights
because set_rights blows away all the RT::IR DutyTeam rights and RT
freaks out when it can't load the Constituency CF during creation.

While in here, clean up RT::IR::Test to just use base and to calculate
what level is needed to export default_agent and rtir_user to (sometimes
it'll be 1, sometimes 2).  This code is stolen from RT::Test.
Catch the remaining GnuPG/SignEncryptWidget

RT 4.2 moved these to /Elements/Crypt/