add db, user registering into db, format

src/app.ml

@@ -0,0 +1,14 @@
+module App_id = struct
+  let qualifier = "org"
+
+  let organization = "Permap"
+
+  let application = "permap"
+end
+
+module Project_dirs = Directories.Project_dirs (App_id)
+
+let data_dir =
+  match Project_dirs.data_dir with
+  | None -> failwith "can't compute data directory"
+  | Some data_dir -> data_dir