GitLab

Turn on free energy plugin by default.
Better rule for when to default build OpenMM wrappers.
Several tweaks to advanced vs. non-advanced cmake variables.

So nightly builds can build CUDA and API wrappers when prerequisites are present.
While still being gentle on third party cmake builders.
New cmake_modules directory contains FindCUDA.cmake from cmake 2.8.0, and
Find OpenCL.cmake from platforms/OpenCL directory.