New Multicontact extension

[GiovanniSalmeri]

Hello everybody. I have unbundled the example that was inside Mailer. Now it is a separate extension Multicontact, but it does nonetheless require Mailer.

It is nothing more than a variation on the standard Contact, with 1. the possibility to choose among several subjects and addresses, 2. an AJAX operation, 3. a somewhat different (simpler?) mode of use. Hope it is useful!