web: Pull docker formatting of CPU and memory into util funcs

Once we start displaying this on the details page we need to
have this be cleaner.
web: Implement changing docker resources while cgroup running

Implement a rudimentary way of changing the memory limit and CPU
priority while the cgroup is running.

Fixes #402
web: Set minimum scales for graph row bars on containers pages

These prevent things like 4 MiB from taking up the whole width
of the column.

Fixes #393