Add memory swap to swarm

Adds support for setting memory swap settings on Swarm services

* Adds flags `memory-swap` and `memory-swappiness` to `docker service
create` and `docker service update` commands.
* Adds compose fields `memswap_limit` and `mem_swappiness` for `docker
stack` commands.

Signed-off-by: Drew Erny <derny@mirantis.com>
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/compose/loader/full-example.yml

@@ -79,6 +79,8 @@ services:
             - discrete_resource_spec:
                 kind: 'ssd'
                 value: 1
+        memswap_limit: 86000
+        mem_swappiness: 27
       restart_policy:
         condition: on-failure
         delay: 5s