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.
fixed recognition cmake file and added ransac_based recognition headers at old locations which include the headers at the new locations and deprecation warnings.
CMake changes were not included in previous commit.  Now they are
recognition/CMakeLists.txt now installs the old header files along side the new ones.  Only the new header files were installed in the previous commit
Use short file names in Doxygen output

We are reaching the filesystem limit otherwise.
Addition of pkg-config header only file generation for geometry lib
Merge pull request #258 from jdt141/master

Addition of pkg-config header only file generation for geometry lib
Merge pull request #246 from jspricke/doxygen_short_names

Short filenames for Doxygen
Added ability to use externally computed normals to supervoxel clustering
This commit fixes #247 - label colors are now created dynamically as needed
Update to issue #247 to avoid breaking api
Merge pull request #264 from jpapon/remove_max_label

Remove max label in supervoxel_clustering
Merge pull request #263 from jpapon/add_input_normals

Added ability to use externally computed normals to supervoxel clustering
add missing stdint.h includes

glibc 2.17->2.18 cleaned some implicit includes in standard headers
again and these two includes were therefore missing to build with
the new lib.
Merge pull request #265 from v4hn/fix-stdint-includes

add missing stdint.h includes
Fix Documentation: sed -i 's/pcd_viewer/pcl_viewer/g'