NURBS fitting: fixed trimming curve for surface fitting (parameter was wrong)
Cleaned up code in B-spline fitting example;
Added tutorial for trimmed B-spline fitting
added saving of trimmed bsplines, added viewer for trimmed bsplines, added saving of bspline in bspline fitting tutorial
Bspline tutorial: reviewed tutorial and added it to the index
Add: create local 2D grid over input point cloud and downsample to minimum z values per grid cell
Merge branch 'grid-minimum' of http://github.com/chambbj/pcl into grid-minimum