[FEATURE]: retrieve files for given molecules

[davidegraff]

Is your feature request related to a problem? Please describe.
Some users have noted that they would like a method by which to programmatically retrieve the in/out files corresponding to a specific compound. They can currently do this themselves by calling VirtualScreen.collect_all() and manually mapping the names of each compound to the collected files and unzipping only those. This is cumbersome.

Desired solution/workflow

# vs: VirtualScreen
# smis: List[str]
y = vs(smis)
best_cpd = smis[np.argmax(y)]
pose_file = vs.get_poses(best_cpd)

Thoughts

• could return the poses as an array of shape p x n x 3, but that would require additional and some custom PDBQT parsing code (MDanalysis doesn't parse multiple models from a single pdbqt from my understanding)
• logically a function of the VirtualScreen?
• should support single or batch retrieval, batch-specific code to come later