Change to make bespoke donation form work with Donate Plus plugin

made OS2 the name value. Made memo the comment value. Made url always point to XBMC.org, since users can't enter a url. Made our method of selecting anonymity translate into the plugin's method. Finally, removed automatic email, as paypal handles email for us.

We can use this one or zag2me's. They both do the same thing. This was mainly a test PR to see if I could actually do it.