Added Organization Manager.

This is a Flamenco/Attract-style Manager object that's instantiated by
the PillarApplication. It can create Organizations and assign/remove
users.

Also I updated the Organization schema to reflect the currently desired
design.

NOTA BENE: this does not include any security/authorisation checks on Eve's
organizations collection.

pillar/__init__.py

@@ -39,6 +39,7 @@ import pillar.web.jinja
 from . import api
 from . import web
 from . import auth
+import pillar.api.organizations
 
 empty_settings = {
     # Use a random URL prefix when booting Eve, to ensure that any
@@ -121,6 +122,8 @@ class PillarServer(Eve):
         # Celery itself is configured after all extensions have loaded.
         self.celery: Celery = None
 
+        self.org_manager = pillar.api.organizations.OrgManager()
+
         self.before_first_request(self.setup_db_indices)
 
     def _load_flask_config(self):