Adds functionality to remove a local template.

This enables the UI to remove existing templates from the file system - something that's been requested for some time now.
Right @warry and I already talked about this and that's why I implemented it already months ago ;-)

I was also thinking an X by each app in the list (terminology point: once we clone the template it's an app not a template). However I think we can't just nuke the directory because you click an X; we have to do a confirmation dialog. I guess it could either say "This will delete ALL FILES underneath /home/myname/xyz. [Cancel] [DELETE THEM ALL]" or it could say "This will forget about application xyz. [ ] also delete files in /home/myname/xyz  [Cancel] [OK]" . The second is what Eclipse does. I don't know what IntelliJ does. If they both do the same I think we should probably stick to that since people are maybe used to it.