build: replace verstion extraction via set to use python The version of roundup was extracted from roundup/__init__.py by sed. It is used to label the roundup.pot template file. Replaced the sed setup by importing roundup and printing the __Version__ variable. This should be less fragile to spacing and other changes.

License
=======

Roundup is Free Software under the following license (from the file
COPYING.txt in the software distribution):

.. raw:: html

   <div class="file_insert">

.. include:: ../COPYING.txt

.. raw:: html

   </div>