use package_data to bundle various data files

* remove generation of MANIFEST.in (only helps for `sdist` command)
* override setuptools' build_py class to filter out directories

Supersedes GH-1215
Fixes ticket:2883
Improve logging of GitPoller when polling lots of branches

This fixes #2946.
Merge pull request #1263 from djmitche/bug2946

Improve logging of GitPoller when polling lots of branches

Fixes ticket:2946
Merge sa2ajj/buildbot:add-package-data (PR #1239)

+autopep8