GitLab

* Unified lots of parallel computation code between platforms

* Unified test code between platforms

* Eliminated duplicated timing code

* Optimize CustomNonbondedForce.updateParametersInContext()

* Optimized uploading changed values to GPU

* Optimized updateParametersInContext() for lots of bonded forces

* Optimized updateParametersInContext() for CustomExternalForce

* Optimized updateParametersInContext() for NonbondedForce

* Code changes for HIP platform

Moved SFMT into libraries folder, and restructured it to allow multiple independent random number generators

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

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

Created a test case for StandardMMForceFieldImpl's findExclusions() method.  Fixed some bugs that it found.  Created a CMake script and configured it for building and running test cases.