Bash command completion for pause and unpause

The docker bash support does not complete `docker pause` and `docker unpause`. This pull request adds the completion. Helper functions to determine the *paused*and the *not paused* running candidates for the completion.
I think this is a little more complicated than it needs to be (especially with a double pipe to sed).  How about something like:
```bash
local names="$( __docker_q inspect --format '{{if .State.Paused}}{{.Name}}{{end}}' $containers | sed 's,^/,,' )"
```

And similarly for `__docker_containers_not_paused`:
```bash
local names="$( __docker_q inspect --format '{{if not .State.Paused}}{{.Name}}{{end}}' $containers | sed 's,^/,,' )"
```