Add ability to store column order

app/models/api/db/Database.model.js

@@ -1,5 +1,6 @@
 const Model = require('flitter-orm/src/model/Model')
 const uuid = require('uuid/v4')
+const ColumnDef = require('./ColumnDef.model')
 
 /*
  * Database Model
@@ -21,6 +22,10 @@ class Database extends Model {
     accessible_by(user, mode = 'view') {
         return user.can(`database:${this.UUID}:${mode}`)
     }
+
+    async get_columns() {
+        return ColumnDef.find({DatabaseId: this.UUID});
+    }
     
     // Static and instance methods can go here
 }