Remove Extras site from p2.inf so JBDS OOTB does not reference the site (and therefore users only see Central for installing 3rd party extras)

Discussion has started regarding the removal of the Extras site URL from JBDS OOTB, so as to encourage users to get their 3rd party bits via Central instead of using the old p2 UI approach.

This would ensure:

a) a cleaner UI experience
b) controlled access to specific groupings of functionality (Central connectors) instead of users being able to pick&choose any feature they want (and therefore get an incomplete experience)

Note that advanced users can still add the Central site or the Extras site once again be able to cherry-pick what they want to install. This just obfuscates it a little.