Display nested containers in the machine view.
More menu items can be disabled.
Disable "Destroy" for deleted machines and containers.
Disable add container more menu on deleted machines.
Don't place units on deleted machines.
Merge pull request #525 from jaycee/do-not-use-deleted-machines

Do not allow units or containers to be added to deleted machines.

* Disable menu items that make no sense for deleted machines (e.g. Add
  container, Destroy)
* Cancel unit placement on machines that are deleted, with notification as to
  why it failed.
Merge pull request #522 from huwshimi/nested-containers

Display nested containers in the machine view

Include nested containers for display in the machine view.
Added sorting for machine tokens.
Added tests for sorting machines.
Added sorting of containers column. Improved efficiency sort/render.
Reselect the active machine token.