Fix: issue 965 speed up clusters extraction

Use patch provided Marvin Gordon to speed up clusters extraction in the loop.
Replce the copy part by a proper constructor improved further the performances.
Update: renice console outputs

Replace std::cout with proper pcl::console::print_*
Add watch to get extraction time
Provide an optional switch "-dump" to write out extracted clusters to "clusters.dat"
Fix: indentation and coding style
Add a workaround for incorrect CUDA_HOST_COMPILER setting

Recent versions of cmake set CUDA_HOST_COMPILER to CMAKE_C_COMPILER
which on OSX defaults to clang (/usr/bin/cc), but this is not a
supported cuda compiler.  This commit adds a workaround to
preemptively set CUDA_HOST_COMPILER to gcc if that compiler exists in
/usr/bin.
organized pcd to png tool
changed description
Removed defines in hog.h.
Added check for OpenNI in CMakeLists.txt (fixed bug 982).
Removed parameters eps and PI from hog.h (used M_PI instead of PI).
Added check for OpenNI in CMakeLists.txt (fixed bug 982).
Fix compilation with Boost 1.53

cf. https://bugreports.qt-project.org/browse/QTBUG-22829