GitLab

Created API and reference implementation of restricting CustomNonbondedForce to selected interaction groups

Converted the routine for identifying molecules from a recursion to a loop.  This avoids stack overflows with very long linear molecules.

AmoebaMultipoleForce did not report particle groups, which could potentially lead to incorrect reordering

Platform specific header files get installed.  This allows plugins to be built with just an OpenMM installation, not a full source tree.