Various changes to support current receiving workflows

i.e. for sake of truck dump, adding child from invoice etc.

tailbone/forms/core.py

@@ -605,6 +605,9 @@ class Form(object):
         else:
             self.enums.pop(key, None)
 
+    def get_enum(self, key):
+        return self.enums.get(key)
+
     def set_renderer(self, key, renderer):
         if renderer is None:
             if key in self.renderers:
@@ -810,6 +813,10 @@ class Form(object):
             except TypeError:
                 return getattr(record, field_name, None)
 
+        # TODO: is this always safe to do?
+        elif self.defaults and field_name in self.defaults:
+            return self.defaults[field_name]
+
     def validate(self, *args, **kwargs):
         if kwargs.pop('newstyle', False):
             # yay, new behavior!