Version 1.1

Updates host_guest_description.md to reflect corrected CB8 phosphate buffer concentration; adds input files (and scripts) from Andrea Rizzi for host-guest challenge reference calculations; adds physical_properties with preview information on the potential physical properties component of the challenge.

These changes add additional information which may be useful but (aside from the phosphate buffer concentration noted in a text document, which has been correct on GitHub since late August) are non-critical.