feat: add basic theme system

This is intended to allow override of look/feel without overriding the
logic/structure of templates.  In practice the main goal internally is
to allow testing of Vue 3 + Oruga, to eventually replace Vue 2 + Buefy
as the default theme.

tests/forms/test_base.py

@@ -11,7 +11,7 @@ from pyramid import testing
 
 from wuttjamaican.conf import WuttaConfig
 from wuttaweb.forms import base, widgets
-from wuttaweb import helpers
+from wuttaweb import helpers, subscribers
 from wuttaweb.grids import Grid
 
 
@@ -25,10 +25,14 @@ class TestForm(TestCase):
         self.request = testing.DummyRequest(wutta_config=self.config, use_oruga=False)
 
         self.pyramid_config = testing.setUp(request=self.request, settings={
+            'wutta_config': self.config,
             'mako.directories': ['wuttaweb:templates'],
             'pyramid_deform.template_search_path': 'wuttaweb:templates/deform',
         })
 
+        event = MagicMock(request=self.request)
+        subscribers.new_request(event)
+
     def tearDown(self):
         testing.tearDown()