Utility scripts to generate VASP inputs

[henriquemiranda]

I have a few scripts that I use all the time with VASP:

1. symmetrize_poscar.py - to symmetrize a POSCAR to primitive of conventional cell using spglib (by default generates conventional cell, -p toggle to generate primitive cell)
2. kmesh_poscar_spglib.py - to generate generalized cartesian meshes KPOINTS files based on a kspacing tag
3. kpath.py - generate KPOINTS file along a path using seekpath

I think these could be useful to other people so it would be nice if we could somehow integrate them inside py4vasp.