Changed json.py to ldt_json.py due to import problem with python json module that now replace django simplejon + started replacing "mimetype" in httpresponses (deprecated) with "content-type" + added fields to forms that didn't declare fields as it's now required by django

Starting upgrading to Django 1.7: removed module-level get_user_model() calls to adjust for new models loading flow + replaced WSFIHandler() with get_wsgi_application()