Add plugin and alias for cleaning docker assets

plugins/available/docker.plugin.bash

@@ -13,6 +13,13 @@ function docker-remove-most-recent-image() {
   docker images | head -2 | tail -1 | awk '{print $3}' | xargs docker rmi
 }
 
+function docker-remove-stale-assets() {
+  about 'attempt to remove exited containers and dangling images'
+  group 'docker'
+  docker ps --filter status=exited -q | xargs docker rm --volumes
+  docker images --filter dangling=true -q | xargs docker rmi
+}
+
 function docker-enter() {
   about 'enter the specified docker container using bash'
   group 'docker'