Prevent Uninstallation

[GoogleCodeExporter]

I'd like there to be prevention of uninstalling the app. Perhaps by having the 
app appear in the list in Location and security > Select device administrators 
and in order to disable it as a device administrator, it require a password.

This would keep anybody using the phone from uninstalling droidwall and messing 
with settings.

Original issue reported on code.google.com by threehappypenguins on 26 Feb 2014 at 7:33