Replace POSCAR with CONTCAR in lobster.py

[naik-aakash]

Changes

1. Replace POSCAR with CONTCAR as default read
2. Change path to explcitly to string (crystaltoolkit serialization fails if taskdoc objects has Path objects)
3. Set default charge back to "Mullkien" as in atomate2
4. Fix LobsterIn doc creation , key names were not correctly filled

Todo

• Update lobsterpy imports to new api

[naik-aakash]

Hi @esoteric-ephemera , I have made minor changes that were needed to also make the objects from taskdoc work as input to the cohp component in crystaltoolkit.

See materialsproject/crystaltoolkit#459

Also, it needs some changes in API of Lobsterpy , cohp module will be deprecated in favor of general coxx module

JaGeo/LobsterPy#428

Some pymatgen PR also needs to be merged before we can release new version of Lobsterpy

These 3

materialsproject/pymatgen#4482
materialsproject/pymatgen#4481
materialsproject/pymatgen#4148