Remove implicit sharing from GeoDataFeature & subclasses

Summary:
Also integrate pimpl classes of more subclasses by subclassing from
GeoDataFeaturePrivate

Implict sharing conflicts with parentship properties on members of
some subclasses

Reviewers: nienhueser, rahn, #marble

Reviewed By: rahn, #marble

Differential Revision: https://phabricator.kde.org/D3316