GitLab

Refactored ForceImpl, lots of KernelImpl subclasses, and other related classes to avoid redundant calculations when requesting a State with both forces and energies

Added a version of Platform::getPlatform() that looks up platforms by name.  Added a Context constructor that allows platform-specific properties to be specified.

Restructured how force and energy computations are done to make it easier to write plugins for the CUDA platform

Optimization: introduced a kernel to clear forces at the start of each time step rather than relying on the stream

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

Modified the initialization order of ForceImpls to prevent them from trying to initialize themselves before the Platform had been chosen

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