[FEATURE]: integrate fpocket (or other pocket/cavity software) to locate candidate box(es)

[alperyilmaz]

Is your feature request related to a problem? Please describe.
There's no problem right now. There's a slight inconvenience about locating the pocket/cavity for Vina. So, pyscreener can integrate this feature so that providing the box can be automated as well

Use-cases/examples of this new feature
The user will provide just a pdb file and smiles formatted ligand and start the docking without worrying about the x,y,z center or size of the box.

Desired solution/workflow
There's autobox example in config samples, however it determines the box location and size by using the ligand in the PDB file (HETATM). This won't work if there's no ligand in PDB file. So, users should provide any PDB file (protein only) and location of the box should be calculated automatically. I suggest fpocket as an option. Since fpocket generates many pockets, best one should be considered for x,y,z center and size extraction.