Allow quip_unified_wrapper to direct output (mainlog) to specific unit
Bugfix for xyz index memory cache
amended README file, put in compiler version requirements
Bug fix to segmentation fault in find_lattice_correspondence()

When max_n_neighbours > l_n_neighbours count(match_list /= 0) is not reliable:
now replaced by count(match_list(1:l_n_neighbours) /= 0).