Order destination groups by parent group, indent subgroups

NB: (Not quite ready for merge yet)

This sorts the destination groups by their parent group, indenting subgroups.

![image](https://cloud.githubusercontent.com/assets/750477/4180887/6e0ad1b4-3707-11e4-9589-cd71f56bc97f.png)

This works because the full name has the parent name first, so the list of full names looks like this:

- Group 1
- Group 1 - subgroup 1
- Group 1 - subgroup 2
- Group 2
- Group 3
- Group 3 - subgroup 3

And the output'll look like this:
- Group 1
-     subgroup 1
-     subgroup 2
- Group 2
- Group 3
-     subgroup 3