Added: Docker state, in e.g. "up 14 hours" format

[ualex73]

Added the "_state" value, giving the "docker ps" output format. I personally this format gives more information then the status like "running", also the uptime gives invalid when a container is stopped (now it gives how long ago it stopped).

[Sanderhuisman]

I rebased the commit onto the last develop branch. Can you explain the conversion function to string format?

I also have to look if the calculation of time delta is correct as the host and container can have different timezones which are both non utc.

[ualex73]

The reason I used the a timezone in the delta, because the e.g. the 'started' value of the container contains a tzinfo/timezone from the 'parser.parser' output:
'started': datetime.datetime(2019, 8, 17, 4, 59, 48, 542645, tzinfo=tzutc())

Also the datetime.now() is normally the local time, without any timezone information. So to match the 'started' tzinfo=tzutc', i added the timezone UTC to my datetime.now() command.
Also, you can't do a delta on a timezone aware and a none timezone aware variables.