Windows 8.1 Universal App Support

This pull request adds Windows 8.1 Universal App Support.

Visual Studio 2013 Update 3 or higher is required to build the Universal App projects.

Please note that EditBox support is missing from the Universal App version and will be added in a separate pull request. 

cocos-console needs to be updated to replace HelloCpp with the project name in the win8.1-universal cpp template.