Instead of removing all the entries in the list store when the set of
installed apps is updated, diff the old and new lists so that removed
apps can be selectively removed from the list store, and added apps can
be selectively added.
This means that we can (in subsequent commits) reload the app list less
conservatively, as doing so will no longer remove in-progress user
modifications to the set of blocked apps. Modifications are still only
saved when the restrict applications dialogue is closed.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Helps: #18, #28
9d4639cf49