Update migration page

Update migration to add styling. Also, use django template and context
to inject variables into the migration page.

See: https://github.com/ansible/awx/issues/8355

awx/ui_next/apps.py

@@ -0,0 +1,10 @@
+# Django
+from django.apps import AppConfig
+from django.utils.translation import ugettext_lazy as _
+
+
+class UINextConfig(AppConfig):
+
+    name = 'awx.ui_next'
+    verbose_name = _('UI_Next')
+