Added C++ project filter file.

Reference: http://stackoverflow.com/questions/1826901/should-i-add-vcxproj-filter-files-to-source-control

VisualStudio.gitignore

@@ -6,6 +6,7 @@
 *.user
 *.userosscache
 *.sln.docstates
+*.vcxproj.filters
 
 # User-specific files (MonoDevelop/Xamarin Studio)
 *.userprefs