Docs: stub for sphinx documentation
inject: better meta class behaviour
PyEntityWithSources: splitt up mixins
core: configure doc strings
docstrings: define docstrings in a central header
setup: configure sphinx build

- build dox with
  python setup.py build_sphinx
PyEntity, PyBlock: use docstrings in bindings
PyBlock: full documentation example
Merge pull request #19 from stoewer/documentation

Documentation using sphinx

LGTM