Added a Database project file to fix iOS Sample.
Added a Database project file to fix iOS Sample.

The sample project didn't previously work on iOS due to the way the
project file was set up. A custom project file has been added to fix the
sample on iOS.

Change-Id: If061eb48011eb553354ec736cce3bb454b7970df

FirebaseExtended/cocos2dx-cpp-sample,FirebaseExtended/cocos2dx-cpp-sample,FirebaseExtended/cocos2dx-cpp-sample,FirebaseExtended/cocos2dx-cpp-sample