Universal task state and name filtering for gcylc.

Via the shared updater rather than tree/list model filtering.
Improved dot updater task_list construction.
Added gcylc tool bar transpose buttons.
Addressed review comments.

Toggle button for graph transpose.
Changed dot view default transposition.
Changed graph view menu item name.
Fixed a doc typo.
Graph view: remove only filtered-out nodes.
Merge pull request #1253 from hjoliver/gcylc.universal-filter

Universal task state and name filtering for gcylc.