Graph and gcylc collapsing: start with vis settings

if defined, otherwise default to initially all collapsed.
Adjust graph command source for previous commit.

Initial collapsed node structure is now handled internally, for graph
command and gcylc graph view.
Updated documentation.
Fix previous change.

The 'group_nodes' list in get_graph_raw() is supposed to hold nodes to
be grouped into their parent nodes (usually from the right-click Group
option), not for the parent nodes themselves.
Merge branch 'master' into gui-collapsed-families

Conflicts:
	lib/cylc/config.py
Replace another doublecircle with tripleoctagon.
Merge pull request #565 from hjoliver/gui-collapsed-families

Repect "[visualization]collapsed families" config item.