shell: Factor out memory info retrieval from cockpit-docker

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Include number of CPUs in machine info

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Add plot.set_yaxis_max

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Scale graph axis according to available CPU and memory resources

But not the big memory graph: It includes swap and the physical memory
limit is thus not appropriate for it.

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Add setup_hook to plot options

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Limit network graph maximum to a resonable minimum

So that we don't show network trickle as if something interesting
would happen.

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Rename cockpit_setup_cgroups_plot to cockpit_setup_multi_plot

It is not only used for cgroups anymore.

Closes #845
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Use consistent ticks for CPU graphs

Reviewed-by: Stef Walter <stefw@redhat.com>