#1021: disallow clock triggers for non-iso8601 cyclers
fix cycling mode string bug
Merge branch '119.iso8601-cycling' of github.com:cylc/cylc into 1021.no_clock_tr_360
Merge pull request #1035 from benfitzpatrick/1021.no_clock_tr_360

#1021: disallow clock triggers for non-iso8601 cyclers