Don't use a Stetic template in the GTK# project template

The Stetic add-in doesn't support F#.
Merge pull request #299 from slluis/remote-stetic-template

Don't use a Stetic template in the GTK# project template
Fixes bugzilla 16695

Simplified match using active patterns
Added null guards to the Project properties
Merge pull request #300 from 7sharp9/bugzilla-16695

Fixes bugzilla 16695