Properly handle ProcessAttribute enabled and default visibility
Summary:
Rather than enabling them always, use column and application visibility
to determnine if an attribute should be enabled. In addition, use a
new visibleByDefault property to set the default visibility state of
columns.
Test Plan:
Start ksysguard, see no plugin provided columns but they can be enabled
from the context menu.
Reviewers: Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: davidedmundson, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D24053