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)
Add a cleanup method to cgroup fs. This will help in building a
standalone cgroup test util. systemd does auto cleanup on empty, so
doesn't need an extra interface.

Docker-DCO-1.1-Signed-off-by: Rohit Jnagal <jnagal@google.com> (github: rjnagal)
Merge pull request #74 from rjnagal/cgroup_testing

Add a cleanup method to cgroup fs. This will help in building a
Merge pull request #67 from vmarmol/api2

Basic version of libcontainer API.
Ignore stats that are not available

Closes #13

Docker-DCO-1.1-Signed-off-by: Victor Marmol <vmarmol@google.com> (github: vmarmol)
Merge pull request #75 from vmarmol/fix-stats

Ignore stats that are not available
Adding Initialize() to create a new container.

Docker-DCO-1.1-Signed-off-by: Victor Marmol <vmarmol@google.com> (github: vmarmol)
Rename package correctly so the binary is nsinit
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Merge pull request #78 from crosbymichael/rename-nsinit-main

Rename package correctly so the binary is nsinit
Merge pull request #76 from vmarmol/api-init

Adding Initialize() to create a new container.