Added nutrient model

command: rails generate redmine_plugin_model body_tracking nutrient
ingredient:references quantity:references unit:references amount:decimal

db/migrate/001_create_units.rb

@@ -19,13 +19,20 @@ class CreateUnits < ActiveRecord::Migration
 
     create_table :ingredients do |t|
       t.string :name
-      t.references :ref_unit
       t.decimal :ref_amount
+      t.references :ref_unit
       t.boolean :hidden
       t.references :source
       t.integer :group
     end
 
+    create_table :nutrients do |t|
+      t.references :ingredient
+      t.references :quantity
+      t.references :unit
+      t.decimal :amount
+    end
+
     reversible do |dir|
       dir.up do
         Unit.create project: nil, shortname: "%", name: "percent"