Update bash completion for "docker run --link" and "docker run -v" to complete on running containers and the local filesystem respectively

Also, add completion for "docker run -a" ("stdin", "stdout", and "stderr"), "docker run --env-file" (local filesystem), and some other minor code style tweaks.

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)