Distance to wheelchairs

[hawesie]

@TobKoer reported the following from the AAF test run:

"We noticed that the robot, when passing by, actually moves very close to persons/wheelchairs. This is rather intimidating for persons sitting in a wheelchair, as the distance is very close and one always has the feeling the robot is going to bump into the wheelchair. So, social distance when passing by should be changed, or the robot should stop"

I don't think we can detect wheelchairs, so this looks like an issue to be solved with the obstacle inflation radius. Related to issue #31.