Move Http calls from OAuth1 providers to OAuth1Client

Add test coverage for default OAuth1Client
Add Integration test for Google login flow

This is to prepare the heavier Oauth2Provider refactoring where we will extract an OAuth2Client
Extract an OAuth2Client shared by various providers
Merge branch 'refactor/extract_oauth_clients' of github.com:jeantil/securesocial into jeantil-refactor/extract_oauth_clients

Conflicts:
	module-code/app/securesocial/core/providers/XingProvider.scala
Merge branch 'jeantil-refactor/extract_oauth_clients'