Update tests to use Django 1.6 test runner

See https://docs.djangoproject.com/en/1.6/releases/1.6/#new-test-runner
Also set DATABASE["TEST_NAME"]

tests/core/tests/__init__.py

@@ -1,6 +1 @@
-from fields_tests import *
-from widgets_tests import *
-from resources_tests import *
-from instance_loaders_tests import *
-from admin_integration_tests import *
-from base_formats_tests import *
+from .test import *

tests/core/tests/test.py

@@ -0,0 +1,6 @@
+from fields_tests import *
+from widgets_tests import *
+from resources_tests import *
+from instance_loaders_tests import *
+from admin_integration_tests import *
+from base_formats_tests import *

tests/settings.py

@@ -27,7 +27,7 @@
     DATABASES = {
         'default': {
             'ENGINE': 'django.db.backends.mysql',
-            'NAME': 'import_export_test',
+            'TEST_NAME': 'import_export_test',
             'USER': os.environ.get('IMPORT_EXPORT_MYSQL_USER', 'root'),
             'OPTIONS': {
                'init_command': 'SET storage_engine=INNODB',