Added libboost-chrono1.53-dev to Travis CI script.
Added boost::chrono to dependency list

* Chrono was added in boost 1.47.0, so changed minimum version to match.
Added FindOpenNI2.cmake search module.

*also added a find_openni2 macro to PCLConfig.cmake.in to allow external users of PCL to find the OpenNI 2 libraries. This is a duplicate of the code in FindOpenNI2.cmake.
Created abstract Image interface for OpenNI grabbers.
Added OpenNI 2 grabber.
Stopped throwing exception on frame sync failure.

* This is not an exceptional event and always occurs for file devices. Print error message instead.
Fixed data race problem with multiple sensors

* The convertTo..PointCloud methods used statically allocated buffers to resize images, causing a data race if multiple deices tried to create point clouds simultaneously. Switched to using member buffers for each grabber.
Fixed warnings in OpenNI 2 grabberModeToOpenniMode

* Fixed assignment in conditional test
* Removed unused argument to focal length getters
* Removed 'register' keywords that do nothing.
Added OpenNI 2 viewer app to visualization module.

* Changed default viewpoint for OpenNI 2 viewer app. Needed to look down +Z axis to see point cloud.
Added HAVE_OPENNI check to people_app

* Depends on pcl/io/openni_grabber.h and does not work with OpenNI 2.x grabber yet
Move common image files to pcl/io/ during the installation; fix block alignments.
Remove hidden assumption that depth source geometry is 640x480
Two cuda device synchronization calls that should not be commented out
Fix an out-of-bounds memory access error
Use the Ptr typedef from the class in CorrespondenceEstimation...::clone. (+1 squashed commit)
Squashed commits:
[501eb1b] Add typename in CorrespondenceEstimation::clone.
Fix compile issue due to an extra semicolon at the end of PCL_DEPRECATED.
Merge pull request #657 from yangyanli/pcl_deprecated_fix

Fix compile issue due to an extra semicolon at the end of PCL_DEPRECATED.
Merge pull request #655 from salino/RegistrationCompilationErrors

Fix for compilation errors in Registration module.
Various doxygen fixes
Merge pull request #654 from VictorLamoine/doxygen_fixes

Various doxygen fixes