Restoring removed packages

- cob_collision_velocity_filter restored
- cob_footprint_observer restored

restored using:

    git checkout 6b644d96 -- cob_collision_velocity_filter
    git checkout 6b644d96 -- cob_footprint_observer

where mas-group/cob_driver@6b644d96045dedec0fe3e9dbf644ae41ef4cf7af
is the parent of mas-group/cob_driver@d69fc623093071a3ec1c0df90e2b3e6283529c3f the commit where the
packages were removed.
Merge pull request #2 from moriarty/minimal_version_for_atwork

Restoring removed packages