Add a "dashboard" like view for showing Nodes X Container insights

[flaviostutz]

Is your feature request related to a problem? Please describe.
When I want to see if everything is OK I have to go to the services list and see status, open tasks list and take look. I don't know if the problems are associated to an specific Node in cluster (may be lack of RAM memory or CPU makes a bunch of tasks to suffer, for example).

Describe the solution you'd like
I wanted a very simple view with Nodes X Containers running in them with visual indications of its status.

Something like the Dashboard we use today:

Describe alternatives you've considered
For a long time we use Swarm Dashboard (https://github.com/charypar/swarm-dashboard) to complement Portainer. We even made some enhancements to it, but it is abandoned and uses the ELM language, which is not very pleasant to write.

Additional context
Some features we'd like on the dashboard that is not present in current implementation is a view of MEM/CPU of each Node on the table header so we can easily correlate restarting/migrating containers with available resources on nodes.

Tell me what do you think about it. I am up to help implement this feature in Portainer :)