start to add a system class for folding plates into platonic solids
the plate folder now seems to be working for tetrahedra
start to make the plate potential a pure c++ potential
the plate potential compiles
add pure cpp plate potential

had to make some other changes

there is now a harmonic interaction c++ potential

simple pairwise and neighborlist potentials now use the
add_energy_gradient functions so can be used in combined potential.

neighbor list potential now uses size_t instead of long int
clean up the plate system class
a few updates to plate folding
forgot to update some files
add test file for harmonic c++ potential
add test for WCAAtomList
add python test for WCAAtomList
add drawing function to plate potential system class
turn off permutations for plate folding
Merge pull request #88 from pele-python/plates

plate folding to platonic solids