Write DockFlow tutorial & files - for a virtual screening

[diegoenry]

A virtual screening with multiple known ligands could be included (maybe also including DUD-E as decoys) must be provided in the tutorial.

1 - Brief DockFlow VS mode description 2 - What's the tutorial about, because we pretend we have no idea about the affinity of most molecules in the library. 3 - That would be useful if we include allow user to include a list of "known binders", basically will be a repetition of DUD-E runs. Than we conclude with a ROC and Ranking curve.