Vacancy: make

** Step 1.** The VacancyGenerator module in pymatgen.analysis.defects.generators is used to generate a set of structures with vacancy.

** Step 2.** If there are init_from_suffix and output_suffix parameter in the properties part, the refine process follows. If reproduce is evoked, the reproduce process follows. Else, the vacancy structure (POSCAR) and supercell information (supercell.out) are written in the task directory, for example, in confs/mp-*/vacancy_00/task.000000.