[SHEPHERD] [PATCH 0/5] Replace 'dmd' service with 'root/shepherd'.

[Alex Kost]

As discussed in a parallel thread, this patchset is for renaming 'dmd'
service to 'root' service (which also provides 'shepherd' name).

Actually, patches 1, 2 and 4 are not related, I just made some changes
that I noticed and I believe should be made :-)

Patches:

[PATCH 1/5] service: Rename 'services' variable to '%services'.
[PATCH 2/5] service: Improve style of 'for-each-service'.

[PATCH 3/5] service: 'service-list' returns unique services.

Without this change, if the root service provides 2 names, 'herd status'
would display:

Started: (root root)
Stopped: ()

[PATCH 4/5] service: Add docstring to 'lookup-services'.
[PATCH 5/5] Rename 'dmd' service to 'root'.