Adding transformations to remove deprecated parameters and to filter documentation strings

This PR adds two new transformations:

* ``deprecated-keyword`` which removes any parameters whose documentation contains the specified keyword which indicates it is deprecated.
* ``filter-documention`` which allows you to specify a regex and a replacement string that will be applied to all documentation strings in the module.

These transformations are being used by the ``ec2`` and ``dynamodb`` models respectively and the updated ``extra.json`` files and resulting models are also included.