Add basic caddy swarm role

Added caddy as swarm container. Uses templated Caddyfile which can be
set up for testing purposes for now.
Depends on docker and docker-swarm, and will keep its stuff where
docker-swarm sets itself up.

site.yml

@@ -0,0 +1,11 @@
+---
+
+- hosts: all
+  roles:
+    - system-upgrade
+    - docker
+    - docker-swarm
+
+- hosts: docker_swarm_manager_node
+  roles:
+    - caddy