klighd.configStore: Cleaning some remainders from ELK migration.
Just removed some debugging relics and commented code from
KlighdLayoutConfigurationStore which was left over from previous
iterations of the ELK migration.
klighd.piccolo: Handle cross-hierarchy edges on collapse.
When collapsing a node, cross hierarchy edges are potentially left
visible. This is now prevented by removing all descendants from the
drawing instead of only children.
klighd.piccolo: Reactivated improved hide/show behavior.
The hide/show methods now utilize the piccolo hidden attribute instead
of removing the PNodes entirely. This prevents change of node order when
drawing overlapping nodes.