Sparse point registration

[raacampbell]

Transform sparse points downsampled to the ARA voxel size using calculated registration parameters. The plugin will do the following:

1. Apply registration coefs to a points file.
2. Saves the transformed points. The user can now overlay the transformed points onto an image stack since we have loaders that do the job.

Eventually we will want a tool to do the inverse transform.

[raacampbell]

Should we bother? This works well in MATLAB.