Clean up a couple more backup functions in the AppCafe:
1) If you try to remove a non-installed PBI, it will simply cancel the installation instead
2) Make sure that if a non-installed PBI is right-clicked, it only shows the "cancel" option.
Make sure that all the other backend functions (desktop/menu/mime/path/auto-update) also only function on PBI's that are actually installed.
Merge branch 'master' of github.com:pcbsd/pcbsd