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/testdata/full-example.json.golden

@@ -181,7 +181,9 @@
                 }
               }
             ]
-          }
+          },
+          "memswap_limit": 86000,
+          "mem_swappiness": 27
         },
         "restart_policy": {
           "condition": "on-failure",

cli/compose/loader/testdata/full-example.yaml.golden

@@ -73,6 +73,8 @@ services:
             - discrete_resource_spec:
                 kind: ssd
                 value: 1
+        memswap_limit: 86000
+        mem_swappiness: 27
       restart_policy:
         condition: on-failure
         delay: 5s