scripts for ZSISA-QHA

[samarerstm]

The following updates have been made:

qha_2D.py
    Added to compute ZSISA-QHA for systems with two degrees of freedom (2DOF).
    Capable of calculating anisotropic thermal expansion and lattice constants for uniaxial configurations.
    Requires PHDOS.nc and DDB files for GSR calculations or _GSR.nc files.
    If PHDOS.nc is available for all structures, normal interpolation for QHA will be applied.
    Supports the use of six PHDOS.nc files for specific structures to employ the E_infVib2​ approximation.

qha_general_stress.py
    Computes thermal stress using EinfVib2EinfVib2​ for specific configurations across various crystallographic structures, from cubic to triclinic.

Please note that these files are not the final versions. I plan to discuss them further with Matteo.