web: Factor cgroup plot setup out of DockerClient.

We'll use this for services also.
web: Add resource graphs to service details.
web: Add "My Services" tab.

Fixes #631
web: Simplify service status display.

By omitting the file status and other redundant information.
web: Add start/stop buttons to My Services
web: Change services terminology.
web: Allow adding and removing of Geard services.
web: Export cockpit.docker to other pages.
web: Include local images in "Add Service" dialog.