Backup volumes from host instead of copying paths

* Backupbot will now copy all volumes from a service with
  backupbot.enabled = 'true' label from the /var/lib/docker/volumes/
  path directly. This reduces the resource overhead of copying
  stuff from one volume to another.
  Recipes need to be adjustet that db-dumps are saved into a volume
  now!
* Remove the Dockerfile and move stuff into a entrypoint. This
  simplifies the whole versioning thing and makes this "just"
  a recipe

Co-authored-by: Moritz < moritz.m@local-it.org>

README.md

@@ -4,7 +4,7 @@
 
 _This Time, It's Easily Configurable_
 
-Automatically take backups from running Docker Swarm services into a volume.
+Automatically take backups from all volumes of running Docker Swarm services and runs pre- and post commands.
 
 ## Background
 
@@ -49,15 +49,13 @@ services:
   db:
     deploy:
       labels:
-        backupbot.backup: "true"
-        backupbot.backup.pre-hook: 'mysqldump -u root -p"$(cat /run/secrets/db_root_password)" -f /tmp/dump/dump.db'
-        backupbot.backup.post-hook: "rm -rf /tmp/dump/dump.db"
-        backupbot.backup.path: "/tmp/dump/,/etc/foo/"
+        backupbot.backup: ${BACKUP:-"true"} 
+        backupbot.backup.pre-hook: 'mysqldump -u root -p"$(cat /run/secrets/db_root_password)" -f /volume_path/dump.db'
+        backupbot.backup.post-hook: "rm -rf /volume_path/dump.db"
 ```
 
 - `backupbot.backup` -- set to `true` to back up this service (REQUIRED)
-- `backupbot.backup.path` -- comma separated list of file paths within the service to copy (REQUIRED)
-- `backupbot.backup.pre-hook` -- command to run before copying files (optional)
+- `backupbot.backup.pre-hook` -- command to run before copying files (optional), save all dumps into the volumes
 - `backupbot.backup.post-hook` -- command to run after copying files (optional)
 
 As in the above example, you can reference Docker Secrets, e.g. for looking up database passwords, by reading the files in `/run/secrets` directly.