DOC : Add a share directory for python_src with an example of conda environnement

python_src/README.md

python_src/share/ex_conda_env.yml

python_src/share/ex_config/ex_config_MultiSlc_CosmoS1SM.json

python_src/share/ex_config/ex_config_MultiSlc_IW.json

python_src/share/ex_config/ex_config_diapOTB_Cosmo.json

python_src/share/ex_config/ex_config_diapOTB_S1IW.json

python_src/share/ex_config/ex_config_diapOTB_S1SM.json