support app:// prototocol in validator for FirefoxOS

[jedp]

Apparently gaia apps give their origin as app://foo instead of http://foo. This does not pass the persona origin validator.

As a result, users will receive a red "There has been an error" message when trying to log in with unverified email and/or forced issuer. The error message will say something about an invalid origin.

I had never noticed this, because building gaia with DEBUG=1 transforms all the app:// origins to http://, and I always build with DEBUG=1 so I can do testing. Such is life.

[jds2501]

I should note that fixing this is required to use persona in a packaged app. So this is definitely a bad bug.