[#4182] Relate deliverables to issues.

db/migrate/006_add_deliverable_id_to_issues.rb

@@ -0,0 +1,12 @@
+class AddDeliverableIdToIssues < ActiveRecord::Migration
+  def self.up
+    # Skip adding the column if it exists from the Budget plugin
+    unless Issue.column_names.include?('deliverable_id')
+      add_column :issues, :deliverable_id, :integer
+    end
+  end
+  
+  def self.down
+    remove_column :issues, :deliverable_id
+  end
+end