Moving to Python to make Windows build scripts more maintainable.
It's intended to be a drop-in replacement, so it should be possible to just switch `.\build-deps.cmd` to `python build-deps.py`, keeping exactly the same arguments and behaviour will be the same.
`build-deps.cmd` is deprecated, but not yet removed, but will be shortly after more testing.
Other batch files will be migrated to Python shortly after too.
* Make possible to invoke run-cmake.bat, build-ifcopenshell.cmd (now bat), install-ifcopenshell.cmd (now bat) directly from File Explorer or command prompt without VS env vars set, if BuildDepsCache file exists, by utilizing CMake's --build functionality. Do not delete CMakeCache.txt always now in order to keep the build options consistent.
* win/readme.md tweaks + make the line width smaller
* Windows batch files: use the last modified BuildDepsCache. Show an error if GEN_SHORTHAND does not exist.