Revert "[hector_nav_msgs] modiefied get Normal service so that it points in acertain direction]"

This reverts commit 2dfdcd33a5512cb3364fa77ee9514a4598d03c05.
hector_nav_msgs: removed yaw member from GetNormal response

yaw is implicitly given by the normal vector
Merge branch 'catkin' of https://hector.gkmm.informatik.tu-darmstadt.de/git/tu-darmstadt-ros-pkg/hector_slam into catkin