Add external compose support in the docker role

- Use ansible.posix.synchronize for compose.yml
- Set fact for compose service restarts
- Introduce plain Docker dev host
- Optionally verify repos via GPG before sync
- Hide docker_repos_path in .folder
- Tweak .env for conciseness
- Add --diff to Ansible in Vagrantfile
- Clean output with loop_control
- Embed GPG in base role

dev/docker.yml

@@ -0,0 +1,8 @@
+- name: Install Docker Server
+  hosts: all
+  become: true
+  vars_files:
+    - host_vars/docker.yml
+  roles:
+    - base
+    - docker