GitLab

* Replace SimTK-containing file headers

* Update file headers for new Tinker reader files added

* Added FAQ links to error messages

* Added missing Windows export

* Added lots of checks for invalid parameter values

* Fixed test failures

* More checks for incorrect parameters

* Fixed test failures

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

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

Changed how kernels get initialized.  StandardMMForceField now has you set the 1-4 interactions explicitly.  CMMotionRemover allows the removal frequency to be set.

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 GBSA kernels, added test case for SHAKE and fixed some bugs in it)