CLEED: at the start, support old and new formats for the input file

[yakutovicha]

We have recently (#37, #41) started building a Python interface to improve the handling of input files. Given the complexity of the process, it makes sense to implement an intermediate stage where both old and new input formats are supported to accelerate development.

This intermediate stage requires creating a converter from the new format to the old format. Once this converter is ready, we can generate old input files using the new format. Subsequently, we will gradually transition the parts of the C code that handle the input to Python.

This issue can be closed as soon as the converter from the new format to the old format is created.