cylc graph, cylc gui: prototype subgraphs
cylc graph, cylc gui: option to switch on cycle point subgraphs
update
Merge branch '119.iso8601-cycling' of github.com:cylc/cylc into subgraph-graphing
update for ctime name change
Merge pull request #1046 from benfitzpatrick/subgraph-graphing

cylc graph, cylc gui graph view: add cycle point subgraphs