The mls_results_ vector did not need to be allocated for most of the
Moving Least Squares methods. However, a reference to an entry in this
vector was needed for calls to computeMLSPointNormal, which is why it
was being allocated in full. This commit causes the vector to be resized
to 1 for those methods that don't need the full version, and then a
reference to entry 0 is passed. The decision was made not to modify
computeMLSPointNormal because it needs to be thread-safe and I do not
have the means to test the OpenMP version of the code. Identical
modifications were made to MovingLeastSquaresOMP::performProcessing as
to MovingLeastSquares::performProcessing.

Tests which do not depend on OpenMP still pass.
Relax requirements of manual_registration and pcd_video_player apps

Both apps are currently under `if (OPENNI_FOUND AND BUILD_OPENNI)`
branch, though they do not actually require openni. This commit moves
them outside of this condition.
Move io_exception.h/cpp out of IMAGE_INCLUDES/SOURCES lists
Merge pull request #785 from mohawkjohn/eliminate_mls_result_resize

Reduced space usage for Moving Least Squares
Merge pull request #798 from taketwo/fix-apps-cmakelists

Relax requirements for manual_registration and pcd_video_player apps
Merge pull request #819 from taketwo/io-exception

Move io_exception.h/cpp out of IMAGE_INCLUDES/SOURCES lists
Add cmake macro to remove VTK definitions.
Remove VTK definitions for CUDA build targets.
Fix compilation of MovingLeastSquaresOMP

import missing variables from super class MovingLeastSquares. Fixes
compiler error introduced in #785.
Merge pull request #825 from jspricke/mlsomp_fix

Fix compilation of MovingLeastSquaresOMP
Fixed the issues with testing the RSD and GRSD features, where the normal estimation was incorrectly asserted
Merge pull request #828 from desinghkar/test_grsd_rsd

Fix #826
Fix dead link in correspondence grouping tutorial
Merge pull request #829 from VictorLamoine/master

Fix dead link in correspondence grouping tutorial
Fix include in 'keypoint.hpp' (2d module)

'pcl/2d/convolution_2d.h' does not exist. Should be 'pcl/2d/convolution.h' instead.
Merge pull request #824 from duga3/fix/vtk6-cuda-compile

Fix compile for CUDA and VTK 6.
Merge pull request #830 from taketwo/fix-convolution-include

Fix include in 'keypoint.hpp' (2d module)
Format code to PCL style
Update code and tutorial
Update tutorial