Re-organizing Dashboard SSO documentation
Re-organizing Dashboard SSO documentation

- Added information about scopes, including our new scope:
  cloud_controller_service_permissions.read
- Split into sections regarding Registering the Dashboard, OAuth2 Login
  Flow, and Reference Implementation sections.

shalako/docs-services,cloudfoundry/docs-services,cwest/docs-services,bridgetkromhout/docs-services