New provider support (Latch) and fix for LightOpenID issue 65

Hello. I've added a new provider, Latch. This is just a single file, and it follows the Stackoverflow/Yahoo OpenID simple form. See latch-app.com for an overview of this new service if you're curious.

I've also fixed LightOpenID Issue #65 (http://code.google.com/p/lightopenid/issues/detail?id=65). It's a one-liner change to hybridauth/Hybrid/thirdparty/OpenID/LightOpenID.php. I've submitted the fix to the LightOpenID project as a gitorious merge request, however I thought you would appreciate it here directly.

This fix restores interop with all OpenID providers, not just Latch. When integrated, it can resolve issue #29 (https://github.com/hybridauth/WordPress-Social-Login/issues/29). I submitted the and LightOpenID fix to the hybridauth library project as well.

I've also submitted the Latch support to the core hybridauth library (additional-providers module). 

Cheers,
Mark