Christian Eichmann

The installed executable was named `spacenav_node` in [CMakeLists.txt:50](https://github.com/ros-drivers/joystick_drivers/blob/foxy-devel/spacenav/CMakeLists.txt#L50), but the launch files tried to call `executable='spacenav'`. I've fixed the spelling in the three launch files and tested them on foxy.

Node composition contributed by @JinyongJeong-Riibotics as part of #59, rebased onto the current master branch - [x] provide both new and old constructor signatures to ensure backward compatibility - [...

Use #59 to support node composition. Need to make sure to not disrupt existing applications.

For `start_angle` and `end_angle`, the documentation states ``` Start angle of scan in radians, if both start and end angle are equal, all angels are regarded. 0° is at the...

### Description According to the code documentation, the TopicMemorySubscriber should never return RUNNING: https://github.com/fzi-forschungszentrum-informatik/ros2_ros_bt_py/blob/fa46148ad8121e47313fbbf8cf130c23245d958f/ros_bt_py/ros_bt_py/ros_nodes/topic.py#L216 But the Node returns `RUNNING` (at least) for the first tick after `_do_reset()` was called, because...