New setup.py and change of layout for the project to be compatible with Python projects

Now MetadataManager and MetaExperiment Tango servers are automatically installed in any Python environment, directly from the setup.py script.

So, it is enough to do:

python setup.py install

or, alternatively, (for development)

pip install -e .

on the project root directory to have the package installed with its dependencies* and the 2 scripts for the Tango servers.

*: only stompest is installed automatically ; other dependencies are PyTango and h5py - those dependencies can be installed automatically once the Conda package is done.

This merge request also makes the final touch from Python 2 to Python 3.