Fix gcylc dot view: wasn't plotting non-family tasks in grouped mode.
Merge pull request #361 from hjoliver/fix-gcylc-dot-view-grouping

Fix gcylc dot view: wasn't plotting non-family tasks in grouped mode.
Add group-all/ungroup-all buttons to the graph view tool bar, and ...

... disable grouping to root level, which is essentially useless.
Merge pull request #362 from hjoliver/gcylc-graph-view-grouping-changes

Add group-all/ungroup-all buttons to the graph view tool bar, and ...