Fix setup.py install

[MedericFourmy]

For now, installing cosypose using python setup.py install or pip install . (equivalent) has 2 issues:

• some of the submodules lack __init__.py files -> easy to fix
• path to local_data folder is assumed to be in the project/package folder (see this line), which is not copied in the installed package (and should not be) -> the local_data path should be specified somewhere at runtime (attribute of cosypose/config.py module?)
• cosypose/config_yann.yaml is also assumed to be present in the installed package but it is not for copied

This PR solves the first issue for now.

NB: python setup.py develop or pip install -e .` works perfectly fine but is normally used while developing the package itself

[nim65s]

Thanks. Can you open an issue for the second part ?