GitLab

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

Examples: now builds CWrappers as a library; modified C builds to use it; added visual studio project to build Argon example in Fortran.
System.h: addForce() wasn't returning the index.

- MingW, where "WIN32" is set by CMake but the compiler is not Microsoft's (should use _MSC_VER) in that case, and 
- in gcc 4.4 which is fussy about some issues that earlier versions were silent about, such as passing a string constant to a "char*" rather than a "const char*".
I also fixed a syntax error in CMakeLists that showed up in the OpenMM workshop for some unknown reason.

Brook is not currently building correctly; I think it has not yet been fully converted to the getTime() interface needed for variable step integrators.

Added doxygenable comment that Langevin friction coefficient is in units of collisions per picosecond (as opposed to picoseconds), which Sherm and I deduced by reading reference implementation and testing extreme values.

(2) I disabled the block of code in the main CMakeLists file that tries to second guess VC++'s choices for runtime libraries. This was required for me to get CUDA to work in VC 2005 where the compiler always chooses multithreaded libraries. I verified that Brook will still build this way, but I haven't tested it.