Change 'tile' keyword to 'token' since there is no 'tile' in mpns api.

Hi,

I came across an issue that there is no 'tile' keyword in the mpns api, the appropriate keyword for tile notifications is 'token'. see: http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh202945%28v=vs.105%29.aspx#BKMK_Tileandtoastnotificationpayloads