GitLab

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

Long range correction for both NonbondedForce and CustomNonbondedForce takes the switching function into account

Moved SFMT into libraries folder, and restructured it to allow multiple independent random number generators

Use a consistent (and more accurate) value for electric constant everywhere.  Also cleaned up handling of constants and units in various places.

Redesigned CustomNonbondedForce to eliminate combining rules and allow the expression to directly use parameters for individual particles.