Rename domain types and fields to be consistent with Facebook API

This issue is to take the opportunity to sync up with Facebook terminology regarding their API.

Renaming types and fields results in breaking changes and normally I'd avoid that or at least deprecate the old names to offer a smooth transition. But Facebook's Graph API v2.0 has forced Spring Social Facebook v2.0.0 into several breaking changes anyway. Therefore, this seems like the best opportunity to sync up the terminology.

Although there are several examples, one obvious one is the domain object representing a Facebook user. Facebook calls it User whereas the Spring Social Facebook type is FacebookProfile. Renaming FacebookProfile to User will result in a more consistent API-to-API Binding experience.