Feature: Document Template Packages

Document Templates can be grouped into a package and generated on-demand
in the same was as individual document templates. Packages can be
generated in bulk.

Disco.Models/Repository/DocumentTemplate/DocumentTemplate.cs

@@ -1,7 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;