Independent builds and python support

This MR introduces various features:

1. This package is now built completely independently of the bob software stack (and bob.conda). It ships its own version of dependencies and can provide better support for python versions that are not necessarily supported (yet) by Bob or BEAT
2. As a bonus, you can now install this package alongside your conda base environment
3. An optimisation during the bootstrap process is now possible since we don't need to install a new environment for bdt using python-3.6, it can just install in the base environment itself.
4. This MR also makes git-clean a bit less verbose, on request form @amohammadi
5. Finally, it fixes #13 (closed), as reported by @heusch

MANIFEST.in

 include LICENSE README.rst buildout.cfg version.txt
 recursive-include doc conf.py *.rst *.sh *.png *.ico
 recursive-include bob/devtools/data *.md *.yaml *.pem matplotlibrc
-recursive-include bob/devtools/templates conf.py *.rst *.png *.ico LICENSE COPYING .gitlab-ci.yml .gitignore *.cfg *.txt *.py
+recursive-include bob/devtools/templates conf.py *.rst *.png *.ico LICENSE COPYING MANIFEST.in .gitlab-ci.yml .gitignore *.cfg *.txt *.py