New: trajkovic and hedley detector 2D
New: port of Trajkovic and Hedley detector to pure geometry
Fix: a silly bug in normals diff computation
Add: pcl_ni_trajkovic application to detect Trajkovic 2D/3D points from OpenNi device
Fix: removal of unused argument and normals_->resize statement
Add savePNGFile function for histograms.

Render the histogram using vtk offline and then save the image to png
file.
PCDGrabberImpl: Add mutex to avoid reentry in trigger()/readAhead() and the resulting race condition.
Bump up PCL version to 1.7.2

1.7.1 has been released already and what people compile from the latest
source is not PCL 1.7.1, but PCL "next".
Merge pull request #590 from taketwo/bump-pcl-version

Bump up PCL version to 1.7.2
Add CentroidPoint class
Add computeCentroid() functions that use CentroidPoint
Extract centroid-related tests from test_common.cpp

There are quite a number of functions dealing with centroid, mean, and
covariance computation. They all are grouped in 'common/centroid.h'
header. Therefore it makes sense to group their corresponding test
functions in a separate file. Hence creation of 'test_centroid.cpp'.
Add unit tests for CentroidPoint and computeCentroid()
In pcl::Feature set output cloud width and height to meaningful values when not specified in input
Merge pull request #591 from sksavant/feature-output-size-pr

In pcl::Feature set output cloud width and height to meaningful values when not specified in input
Fix obscure MSVC error
Add: progressive morphological filter to extract ground returns
Merge pull request #574 from chambbj/progressive-morphological-filter

Add: progressive morphological filter to extract ground returns
Add: filter to remove locally maximal points
Merge pull request #577 from chambbj/filter-local-max

Add: filter to remove locally maximal points in the z dimension