Support mailing OASIS managers with osg-notify

In case of issues or maintenance of the OASIS stratum 0/1, we would like to notify all OASIS managers. You would think that we get this for free with our support for notifying different VO contact types but the OASIS manager list is not part of the VO contact list. And since osg-notify uses the XML, we can't change the data structure to something more sensible.

I'd like to see oasis added as a choice for the oim-contact-type option that allows a user to send notifications to OASIS managers.