- Add the option of specifying the externals path
- Add V8P5 support
- Python launcher is no longer required, batch files wrapping Python scripts are used instead
- As such, Python is no longer required: the embeddable version is downloaded and used instead
- pysource batch files are now generated on the fly
- Add PyQt5 as a backend for Matplotlib

Versions 5.1.1 of METIS and 1.3.0 of libaed2 lead to crashes.
Also:
- Fix HDF5 and MED versions in pysource batches
- Upgrade Mingw version to the latest stable (12.2)