feat: refactor forms/grids/views/templates per wuttaweb compat

this starts to get things more aligned between wuttaweb and tailbone.
the use case in mind so far is for a wuttaweb view to be included in a
tailbone app.

form and grid classes now have some new methods to match wuttaweb, so
templates call the shared method names where possible.

templates can no longer assume they have tailbone-native master view,
form, grid etc. so must inspect context more closely in some cases.

tests/test_config.py

@@ -0,0 +1,12 @@
+# -*- coding: utf-8; -*-
+
+from tailbone import config as mod
+from tests.util import DataTestCase
+
+
+class TestConfigExtension(DataTestCase):
+
+    def test_basic(self):
+        # sanity / coverage check
+        ext = mod.ConfigExtension()
+        ext.configure(self.config)