Allow monitors to be cloned

[kid4git]

It would be very helpful to be able to clone/duplicate monitors including triggers and actions. Some monitors really just differ in a query condition and some action subject, but it's tedious and takes minutes to create them with basically the same configuration as an existing one.

I tried cloning via API by getting the existing one with GET _opendistro/_alerting/monitors/<monitor_id>, stripping IDs and then posting as a new one with POST _opendistro/_alerting/monitors, but this creates unusable monitors as

• in the monitor definition, the original visual graph is turned into an extraction query, changing this to a visual graph leaves me with an empty time field select box and thus an empty query
• the same is true for the trigger definition which now shows the fields "Extraction query response", "Trigger condition" and "Trigger condition response" instead of the "Trigger condition" select box and the query graphic .