Matt 'Cleaned up' GatewayFormChooser aka Went Crazy

Uhh... so ya... only needed to allow gateway filtering and then
decided things looked ugly... Not sure if this ended up any better
though.

Change-Id: Ib61d1486806b9cce4e39cadfadf8e83c22fd4692
Allow the Form Chooser to know about Currencies :)

The Form Chooser can now add '+' rules if they aren't explicitly
specified that detail all about the currencies an adapter can
accept.

Change-Id: I45dcd60433a2bedcb7157a30d095dbcec08bccda