GitLab

Changed how kernels get initialized.  StandardMMForceField now has you set the 1-4 interactions explicitly.  CMMotionRemover allows the removal frequency to be set.

1) Added DLL export macros to many classes; enough to get tests to compile
2) Cosmetic changes to reduce warnings in Visual Studio:
   a) change many "for (int i ="... to "for (size_t i ="... to avoid unsigned mismatch warnings
   b) included many explicit static_cast<OpenMMReal>() casts to document places where double->float conversion warnings occur

Continuing to implement ReferencePlatform (implemented GBSA kernels, added test case for SHAKE and fixed some bugs in it)

Continuing to implement ReferencePlatform (implemented kinetic energy calculation and LangevinIntegrator)