move git clone from daemon to client

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)

add a little doc
if client has no git, use server

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Add initial logging to libcontainer
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Add stderr log ouput if in debug
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Fix `docker cp` trying to untar files that do not exist.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <erik@hollensbe.org> (github: erikh)
Merge pull request #4645 from crosbymichael/add-logger

Add logger to libcontainer
Merge pull request #4364 from vieux/move_clone

move git clone from daemon to client
Merge pull request #4701 from erikh/4099-non_existent_file_no_error

Fix `docker cp` trying to untar files that do not exist.
Move networking drivers into runtime top level pkg
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Move execdrivers into runtime top level pkg
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Move graphdrivers into runtime top level pkg
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Gofmt imports
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #4678 from crosbymichael/move-runtime-deps

Move runtime deps