experimental support for rcc files loading in kpackage

Summary:
support for the contents/ directory of kpackage to be
compressed in an rcc file, new cmake macro
kpackage_install_bundled_package which generates it,
the old install package is unaltered for better retrocompatibility

Test Plan:
most of plasma ui works correctly, plasmoids can be migrated
safely, some other things may still require adapting as
setSource(QUrl::fromLocalFile(package.filePath("mainscript"))
must be changed to
setSource(package.fileUrl("mainScript"))

Reviewers: Plasma, davidedmundson

Subscribers: davidedmundson, apol, plasma-devel, Frameworks

Tags: Plasma, Frameworks

Differential Revision: https://phabricator.kde.org/D9197