use full dotted paths for all archivebox imports, add migrations and more fixes

archivebox/api/apps.py

@@ -5,6 +5,7 @@ from django.apps import AppConfig
 
 class APIConfig(AppConfig):
     name = 'archivebox.api'
+    label = 'api'
 
 
 def register_admin(admin_site):

archivebox/api/v1_workers.py

@@ -94,7 +94,7 @@ class OrchestratorSchema(Schema):
 @router.get("/orchestrator", response=OrchestratorSchema, url_name="get_orchestrator")
 def get_orchestrator(request):
     """Get the orchestrator status and all worker queues."""
-    from workers.orchestrator import Orchestrator
+    from archivebox.workers.orchestrator import Orchestrator
     from workers.worker import CrawlWorker, SnapshotWorker, ArchiveResultWorker
 
     orchestrator = Orchestrator()