D26466: Update KPluginSelector to allow KCM to show good state for reset, apply and default button

[Benjamin Port]

bport added a dependent revision: D26467: KCM runners: fix default button.

REPOSITORY
  R295 KCMUtils

REVISION DETAIL
  https://phabricator.kde.org/D26466

To: bport, #plasma, ervin, crossi, meven
Cc: kde-frameworks-devel, LeGast00n, GB_2, michaelh, ngraham, bruns