use new property plasmoid.editMode
Summary:
toolboxes set editmode by themselves
possible for toerh things to trigger edit mode now
Test Plan: handles open correctly
Reviewers: Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D5154