Added missing word and link

Based on the keypoints found we have to +extract+ features (linked tutorial which explains how features work in pcl)
Dual quaternion transformation estimation algorithm added
dq renamed to dual_quaternion;
tests added
dual quaternion precision changed to double to pass the tests
Remove shared_ptr from param_k_ and param_radius_

fixes segfault im lum
Add an overload of pcl::io::savePNGFile().

The new function takes sensor_msgs::Image and saves it as a PNG file.
Currently supported are "rgb8", "mono8", and "mono16" image encodings.
Add PointCloudImageExtractor base class and several implementations.

* PointCloudImageExtractorFromRGBField produced a color image based on
  the data in "rgb" field of a point cloud.
* PointCloudImageExtractorFromNormalField produced a color image based on
  the data in "normal" field of a point cloud.
* PointCloudImageExtractorFromLabelField produced a mono image based on
  the data in "label" field of a point cloud.
* PointCloudImageExtractorFromZField produces a mono image based on the
  "z" field of a point cloud.
* PointCloudImageExtractorFromCurvatureField produces a mono image based on the
  "curvature" field of a point cloud.
* PointCloudImageExtractorFromIntensityField produces a mono image based on the
  "intensity" field of a point cloud.
Add an overload of pcl::io::savePNGFile().

The new function takes a field name and uses appropriate
PointCloudImageExtractor subclass to extract an image from the given
field. Currently supported are "normal", rgb", "label", "z",
"curvature", and "intensity" fields.
Add pcd2png application to the "tools" module.
Add tests for Point Cloud Image Extractors.
Fix a bug in RegionGrowing with oversized output cluster vector.

The clusters vector output by RegionGrowing<PointT, NormalT>::extract()
function was not properly trimmed after filtering out clusters that are
too small and too large. As a result many dozens/hundreds of zero-sized
clusters seeped into the output vector.
Added vtkPolyLine.h header to example_supervoxels.cpp

In 1.7.0 the supervoxel example doesn't build with Visual Studio 2012 (and others: https://github.com/PointCloudLibrary/pcl/issues/202).
Only build pcd_select_object_plane.cpp when QHull is available

As pcd_select_object_plane.cpp requires QHull it should be excluded when QHull is not found.
Check to only build in_hand_scanner when OpenNI is available
fixed memory leak
Switched from gl.h to qgl.h
Merge pull request #211 from henningpohl/patch-6

Switching from gl.h to qgl.h
Merge pull request #208 from henningpohl/patch-3

Check to only build in_hand_scanner when OpenNI is available
Merge pull request #207 from henningpohl/patch-2

Only build pcd_select_object_plane.cpp when QHull is available
Merge pull request #206 from henningpohl/patch-1

Added vtkPolyLine.h header to example_supervoxels.cpp