remove `vision_utils/` from the path found by Findvision_utils

We currently use vision_utils in some wolf plugins. In particular, in plugin vision, we find the following:

#include <sensors.h>

which compiles!!! But who would know that this file is part of vision_utils? What if another robotics lib has the same file name somewhere?

I think this is bad and dangerous. I propose the following as default:

#include <vision_utils/sensors.h>

This would require an update in the Findvision_utils.cmake file shipped with the library.

EDIT (@jvallve)

There are some problems in finding the libvision_utils.so in runtime. After some research, we consider that the easiest way to address this is change the destination of that file to usr/local/lib instead of creating the folder vision_utils there.

This would also imply changing Findvision_utils.cmake so everything could be done in the same MR.