feat(worker): load config using shared helpers

BREAKING CHANGE: The worker `RMQ_CONFIG_FILE` environement variable has
been renamed to `LIBRETIME_CONFIG_FILEPATH`. In addition the systemd
working directory for the worker has changed from `/srv/airtime` to
`/var/lib/libretime/worker`.

worker/setup.py

@@ -24,9 +24,13 @@ setup(
     install_requires=[
         "celery==4.4.7",
         "kombu==4.6.10",
-        "configobj",
         "mutagen>=1.31.0",
         "requests>=2.7.0",
     ],
+    extras_require={
+        "dev": [
+            f"libretime-shared @ file://localhost{here.parent / 'shared'}",
+        ],
+    },
     zip_safe=False,
 )