GitLab

Modified the API for lots of classes so that the number of particles/bonds/etc. need not be specified in the constructor.

Checked in explicit solvent implementation for Cuda platform (cutoffs, periodic boundary conditions, SETTLE)

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