Fix for LaunchPad Bug #1015832 - Update Manager not reporting updates

It has been noticed that when the Update Manager is running in the system tray, it does not report available updates until the user manually opens the Update Manager. I found this was due to mintUpdate initially running in user mode, which lacks the permissions to update the APT cache.

These changes fix this by setting up sudoer rules which allow the user to run the checkAPT script via sudo without a password. The sudoer file includes the full pathname, so only the checkAPT script in the system location can run without a password. This allows the Update Manager to always be able to update the cache, even in user mode.

Geoff