* api/client/ps.go: Refactor CmdPs to use a fields list of characters to determine which columns to print on `docker ps` invocation. This adds an ability for the docker command to print the columns of output in arbitrary order. Signed-off-by: Jeff Mickey <j@codemac.net> Docker-DCO-1.1-Signed-off-by: Jeff Mickey <j@codemac.net> Upstream-commit: de0e883331c85cc7617184900369e1ec9f723b6c Component: engine