Implemented Modeller.addExtraParticles().  Also some cleanup in ForceField.
Implemented serialization for Drude plugin
ForceField supports DrudeForce
Merge pull request #4 from peastman/master

Most of the features to support Drude particles are now complete and functional
first working version with shuffle - but breaks lots of existing tests
Fixed bug in CustomIntegrator's handling of massless particles (see bug 1871)
Fixed errors in DrudeLangevinIntegrator in mixed or double precision mode
Created DrudeSCFIntegrator, including reference implementation
Merge pull request #5 from peastman/master

Fixes to a couple of bugs (in CustomIntegrator and DrudeLangevinIntegrator)
Fixed linker errors on Windows
Merge pull request #6 from peastman/master

Fixed linker errors on Windows
Created CUDA implementation of DrudeSCFIntegrator
nonbonded.cu will now use shuffles on sm_30 or higher
Merge branch 'master' of https://github.com/SimTk/openmm
bugfix to ifdef conditions in nonbonded.cu
minor bug fixes
Fixed debugging commits
Merge pull request #7 from proteneer/master

Nonbonded.cu now uses shuffle intrinsic
Merge branch 'DrudeSCFIntegrator' of https://github.com/peastman/openmm
Created OpenCL implementation of DrudeSCFIntegrator