Custom cgroup path

[flxo]

Add an option to define a custom cgroup name for a container. The default is currently a top level cgroup called ` and a single level subdir underneath.

Add the possiblity to either provide a full path and/or a relative to the northstar top level group.

e.g:

cgroups:
    group:
          path: subdir/containername
          relative: true # results in <name from config>/subdir/containername
or
         path: containername # containername
         relative: false
    memory:
      memory_hard_limit: 10000000
      swappiness: 0
      attrs: {}