Port a bunch of classes away from Plasma::Package
Summary: Ported away some classes, removes many unneeded casts that happen when starting.
Test Plan: Tests still pass, plasma starts properly
Reviewers: Frameworks, Plasma, mart
Reviewed By: Plasma, mart
Subscribers: davidedmundson, mart, plasma-devel
Tags: Plasma, Frameworks
Differential Revision: https://phabricator.kde.org/D6041