Allow the usage of mako templates

Mako is a python 2.6->3.x compatible
templating engine, allow its optional
usage (until we can depricate cheetah)
by allowing for specifying a template
file header that can define which template
engine to use. 

For now support cheetah (the default) and
if specified support mako as well.
Switch to jinja & adjust tpls
Add some basic template tests
Add basic renderer support and more robust import handling
Log the renderer type when rendering files
Add non braces matching and a few more tests
merge from trunk
use textwrap, simple formatting improvement.
add package info for bddeb/brpm
Allow the usage of jinja2 templates

This drops the hard requirement on Cheetah.

Jinja is a python 2.4->3.x compatible templating engine, allow its
optional usage (until we can depreciate cheetah) by allowing for
specifying a template file header that can define which template engine to
use.

If the template file header does not specify a renderer, then assume
that that is cheetah.  If cheetah is not available, then use a limited
builtin renderer on a best effort basis, and log the warning.