Basic version of libcontainer API.

This version has mostly the behavior available today and the
functionality agreed upon in other PRs. Further changes will be sent as
smaller PRs for discussion.

Docker-DCO-1.1-Signed-off-by: Victor Marmol <vmarmol@google.com> (github: vmarmol)
Update api proposal

Move concepts into specific files for easy management
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: vmarmol)
Merge pull request #67 from vmarmol/api2

Basic version of libcontainer API.