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.
Added common search path for deb packages.

* /usr/include/openni2 is a common install location for unofficial OpenNI2 deb packages.
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
add real fps (kinfu)
New tutorial: PCL visualizer in Qt with cmake
Fix pairwise incremental registration order of application of cumulative transforms
Fix compiler warnings (reorder, unused) in Openni2
Revert merge pull request #528

This reverts commit 70a9b93c6c0cb6d2666422905340a1708e694319, reversing
changes made to ec9d63dae69778f2cbeba86d7c33d4b872dcce2f.