NLC for 2D heis *seems* to be working now.  At least the answers are reasonable.

Added order16rectangles_heis.dat: includes only rectangles with even # of sites in the usual order.
order16rectangles_heis_ordered.dat has the even rectangles ordered by number of sites.
Merge branch 'master' of github.com:MelkoCollective/NLC_Heis_Bilayer