Use default C++ and boost::placeholders::_N instead of deprecated _N

[lucasw]

The default C++ will be 14 in noetic Ubuntu 20.04, 17 or later on newer systems- 17 is necessary to avoid issues with log4cxx 0.12.

OgreVector3.h is deprecated in newer Ogre versions, a helper file is present in the latest rviz https://github.com/ros-visualization/rviz/pull/1741 (so none of this can be released until rviz with that new header file is released)- I can separate this out into a different commit/PR if desired.

My text editor added newlines to last lines of the files I edit, I can remove those if desired.

[maximilianwulf]

Thank you, should be fine. Processing it with the team.