[kcms/keys] Highlight changed settings

Manual implementation of change highlighting as done automatically in other
kcms. Highlighted items include: Collpased action delegates whose active key
sequences are different from the default, in the expaned state unset checkboxes
for default key sequences and keysequenceitems for added shortcuts are highlighted.
Finally in the components list, delegates who contain at least one action that is not
in a default state are higlighted in the same style as config modules in the
system settings sidebar.