costmap_2d: fix radius warning when footprint is set

If the footprint parameter is set, inscribed and circumscribed radii are
computed from that. However, the check was done *before* that
computation and therefore used the default params. This commit

- moves the check after the computation
- changes the wording from "inscribed and circumscribed radii" to
  "inscribed or circumscribed radius".
costmap_2d: output radius values in warning
Merge pull request #43 from mintar/costmap2d_radius_warning

costmap_2d: fix radius warning when footprint is set