Changed hog class with a new optimized version which exploits SSE2 operations (3x speedup in descriptor computation).
Fixed bug multiple definitions of hog (moved hog.hpp to hog.cpp).
Bug fixed in hog.g: clip_ variable changed from bool to float.
Added non-SSE version of the hog code.
Removed some compilation warnings from people module.
Merge remote-tracking branch 'mmunaro/master'

Conflicts:
	people/include/pcl/people/impl/hog.hpp
	people/include/pcl/people/impl/person_classifier.hpp
Rename old ROS components (sensor_msgs/*)

std_msgs::Header -> pcl::PCLHeader
sensor_msgs::Image -> pcl::PCLImage
sensor_msgs::PointCloud2 -> pcl::PCLPointCloud2
sensor_msgs::PointField -> pcl::PCLPointField
Took out all USE_ROS references
Move conversions into common/pcl

fromROSMsg -> fromPCLPointCloud2
toROSMsg -> toPCLPointCloud2
Remove pcl_2d and dependent files
Remove pcl_cuda
Remove pcl_gpu
Remove CUDA related cmake stuff
Remove pcl_ml and dependent files
Remove pcl_simulation
Remove pcl_stereo
Remove 3rdparty stuff
Remove Brisk keypoints and features because there is no non SSE4 version