Support debugging in MN4

[polsm91]

Having two hecuba installations at the same time is wrong and leads to problems (incoherency, bugs,...) and slow development.

However, Hecuba dependencies such as Cassandra4slurm, the Python drivers and others are installed in the same folder as Hecuba in MN4 (and many others). Therefore, we need a way to enable users to install and debug with Hecuba in the home folder without having to manually install all dependencies.

The current workaround is to append the Hecuba egg path to LD_LIBRARY_PATH and PYTHONPATH