feat: add ability to set container config options during create/clone/upgrade actions

Also add to documentation where possible.

Closes dokku/dokku-mongo#131

subcommands/create

@@ -18,6 +18,7 @@ service-create-cmd() {
   #E export ${PLUGIN_DEFAULT_ALIAS}_CUSTOM_ENV="USER=alpha;HOST=beta"
   #E dokku $PLUGIN_COMMAND_PREFIX:create lolipop
   #A service, service to run command against
+  #F -c|--config-options "--args --go=here", extra arguments to pass to the container create command
   #F -C|--custom-env "USER=alpha;HOST=beta", semi-colon delimited environment variables to start the service with
   #F -i|--image IMAGE, the image name to start the service with
   #F -I|--image-version IMAGE_VERSION, the image version to start the service with