* Add RC test app.
* Add private header files to podspec used by 2P.
* Rename FIRRemoteConfig_Internal.h to FIRRemoteConfig_Private.h.
* Fix style.
* Add copyright notice.
* Fix relative path to RCNConfigSettings for tests.
* Fix style.
* Rename to FIRRemoteConfig_Private.h for unit tests.
* Rename to coorect relative path.