[FEATURE REQ] add monitoring of system resources given docker container id

[MadhavJivrajani]

Is your feature request related to a problem? Please describe.
Given that functionality for resource monitoring is provided on a per-process basis, I think it'd be super cool to have this feature for Docker containers as well.

Describe the solution you'd like
grofer docker --cid cid
grofer export --cid cid

Proposed solution
Gopsutil provides good support for getting info about containers.

Beyond this, the extended proc functionality of gopsutil can be used by obtaining the PID from the container ID by running something like docker inspect -f '{{.State.Pid}}' <Container ID>

Additional context
Need to see if information for all the currently provided widgets is obtainable.