Give the controller type as parameter in ctrl namespace

[christophfroehlich]

This changes the location of declaring the controller type, which will be possible with ros-controls/ros2_control#1502

I tried to write it consistently:

• Controller types without parameters are declared in the controller_manager namespace (joint_state_broadcaster)
• Others are declared in the controllers' namespaces, which is considered to be best-practice from now on.

[saikishor]

@christophfroehlich Thanks a lot for helping :)

[christophfroehlich]

Needs ros-controls/ros2_control#1640 to work with example_15

[saikishor]

LGTM now!