Initial implementation.
Fix shutdown hang and add to test battery.
Assign correct db as "primary"
Merge remote branch 'upstream/master' into cylc6.viewable-db
cylc scan: scan multiple hosts

Scan all monitored hosts by default.
Merge remote branch 'upstream/master' into cylc6.viewable-db
Back compat.
cylc restart: fix 'runahead' state handling
Merge pull request #1193 from benfitzpatrick/restart-runahead

cylc restart: fix 'runahead' state handling
Merge pull request #1189 from matthewrmshin/cylc-scan-hosts

cylc scan multiple hosts
Handle exception raising.
allow prev point format with prev icp
Merge pull request #1194 from benfitzpatrick/prev-point-format-prev-icp

Allow prev-format `initial cycle point` with prev `cycle point format`
Merge pull request #1173 from arjclark/cylc6.viewable-db

cylc 6 -  second db