Adds more documentation for labels and adds the label instruction to the
man-pages.
Also included is a document called "Labels - custom meta-data in Docker"
in the user-guide, this is still a work-in-progress I started to describe
the "namespaces" conventions, an example on storing structured data.
I ran a bit "out of steam" (writers block?) on that document, but kept
it in (for now), in case it still ends up useful.
The Remote API documentation changes will need to be moved to the
docker_remote_api_v1.18.md document when rebasing the whole PR.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Signed-off-by: Darren Shepherd <darren@rancher.com>
Mary Anthony