use libusb's pkgconfig support

This streamlines sick_tim's libusb detection.
add missing external dependencies

make sure msg headers are built before sick_tim_3xx
install meshes & urdf
export headers related to libsick_tim3xx

As far as I know nobody uses them right now,
but as we install the library, why not provide the interface?
mark libsick_tim_3xx as exported
Merge pull request #16 from v4hn/hydro_catkin_fixup

fixup hydro catkinize
Merge pull request #15 from v4hn/libusb-pkgconfig

use libusb's pkgconfig support