Auth Adapters refactoring (#3177)

* Moves all authentication providers to Adapter/Auth

* refactors specs

* Deprecates oauth option in favor of auth option

- Deprecates facebookAppIds option (in favor of auth.facebook.appIds)
- Adds warnings about the deprecated options

* nits

spec/support/CustomAuthFunction.js

@@ -0,0 +1,14 @@
+
+module.exports = function(validAuthData) {
+  return {
+    validateAppId: function() {
+      return Promise.resolve();
+    },
+    validateAuthData: function(authData) {
+      if (authData.token == validAuthData.token) {
+        return Promise.resolve();
+      }
+      return Promise.reject();
+    }
+  }
+}