connect groupbox toggles to change signal
Summary:
the bridge, ppp, and gsm settings contain qgroupboxes which previously
were not tracked
e.g. the STP box toggle on bridges didn't enable the apply button
since checkable qgroupboxes are a fairly generic concept, let's connect a
generic watch rule
Test Plan: toggling STP in bridge settings actually enables apply button
Reviewers: jgrulich!
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D25368