Add Developer Certificate of Origin Text

We purposely chose to license Docker under the Apache 2.0 license. This is a well-known
license, which is popular for its permissive and flexible properties, while still
encouraging a collaborative community. It also makes certain representations with regard
to contributions, and the rights given to contributors, the project, people who use Docker,
people who modify Docker, etc.

This approach to contributions is inspired by the popular Linux Developer
"Certificate of Origin". This approach makes it simple for new contributors to get started,
and avoids bureaucracy in tracking contributions and contributors.

To indicate accordance, each individual contribution to the Project is signed off by the
developer, using his or her real name, email address, and github handle in the format below:

	Docker-DCO-1.0-Signed-off-by: Joe Smith <joe.smith@email.com>
Increase max image depth to 127
Merged with master
added authConfig to docker build
Simplify and resync hack/make/test and hack/make/dyntest output handling
Clean output and simplify hack/make/*test by adding go_test_dir function in make.sh
Add much better pruning of non-tested directories, including pruning the integration tests directory (doing more with "find" and nothing with "grep")
Unify hack/make/*test further by invoking hack/make/test directly from dyntest
hack/PACKAGERS.md: libdevmapper
Unify dyntest/test and dynbinary/binary hack bundlescripts further by cross-invocation and keeping all the logic in one place, taking advantage of LDFLAGS_STATIC that is the only bit that gets replaced for dyntest/dynbinary
Add separate "test-integration" bundlescript (and corresponding dyntest-integration bundlescript)
refactor and fix tests
fix docker images -tree <invalid_image> and docker images -viz <image_name>
fix size in -tree
Update mkimage-debootstrap with even more tweaks for keeping images tiny by more aggressively removing cache files and by not downloading apt-cache Translations files
Engine: integer job status, improved stream API

* Jobs return an integer status instead of a string
* Status convention mimics unix process execution: 0=success, 1=generic error, 127="no such command"
* Stdout and Stderr support multiple thread-safe data receivers and ring buffer filtering
Engine: new command 'stop' gracefully stops a container.
move t from arg to env
Fix volumes on the host by following symlinks in a scope
Improve FollowLink to handle recursive link and be more strick