Add root version of drive-harddisk
I did not add drive-harddisk-home in this commit because it was simply too difficult to make an easily readable symbol for home on the 16px version.
Reviewers: VDG, ngraham
Reviewed By: VDG, ngraham
Subscribers: ngraham, kde-frameworks-devel
Differential Revision: https://phabricator.kde.org/D16633