Added imageURI to blog-post model

We have always been parsing image URIs out of blog posts, but up until
now I had forgotten to add them to the actual database.

Author: dannybrown

src/database/models/blog-post.js

@@ -20,6 +20,11 @@ const blogPostDatabaseDefinition = database.define('blog_post', {
     field: 'link',
     allowNull: false
   },
+  imageURI: {
+    type: Sequelize.STRING,
+    field: 'image_uri',
+    allowNull: true
+  },
   description: {
     type: Sequelize.TEXT,
     field: 'description',