- fixed cache code to work with Beaker 1.0.1, which is now the required version of Beaker.
- removed unnecessary attributes from DefTemplate.
- added ModuleTemplate class, which allows the construction
of a Template given a Python module generated by a previous
Template.   This allows Python modules alone to be used
as templates with no compilation step.   Source code
and template source are optional but allow error reporting
to work correctly.