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.
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
Merge pull request #409 from nizar-sallem/trajkovic

Trajkovic
Merge pull request #528 from sksavant/histogram-save-pr

Add savePNGFile function for histograms.