Revert "Fix for Windows Phone 8 template."

This reverts commit 56dd0d7b6d60f8f2353c7e781751fadd79faea57.
Adds the default constructor for TouchCollection.

Without this constructor the TouchCollection class, since is a struct
and don't need to be instantiated, can throw some exceptions when you
call, for example, the Count method. This assures full XNA
compatibility.
Error checking for _collection.