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
Merge pull request #164 from jspricke/remove_ros

Remove ROS