Merge HGFlow into ChemFlow

[diegoenry]

HGFlow came from two separate projects. Paulina and I had different do-it-all scripts but we rewrote it together to a single and more powerfull one.

Naturally HGFlow example files will come from SAMPL4 5 and 6 challenges and we should keep updating it.

In the NEAR future HGFlow outputs will be part of the HostGuest database (HGBase), our website with ALL well standadized free energy runs and results.