Disabled new Bookshelf fetch behaviour across models

- as per https://github.com/bookshelf/bookshelf/wiki/Migrating-from-0.15.1-to-1.0.0#default-to-require-true-on-modelfetch-and-collectionfetchone, models will now default to `{require:true}` during a fetch, which changes how Bookshelf will respond when a models yields no results
- instead of passing a `null` result, it will reject with an error, so we'd need to switch to `.catch`ing everything
- our code is set up to handle all these null results and switching style is not currently on the cards so we want to use the existing behaviour for now
- to enable this, the `requireFetch` option needs to be added to the model definitions

core/server/models/base/index.js

@@ -21,6 +21,8 @@ ghostBookshelf.Model = ghostBookshelf.Model.extend({
     // Bookshelf `hasTimestamps` - handles created_at and updated_at properties
     hasTimestamps: true,
 
+    requireFetch: false,
+
     // https://github.com/bookshelf/bookshelf/commit/a55db61feb8ad5911adb4f8c3b3d2a97a45bd6db
     parsedIdAttribute: function () {
         return false;