Add support for initial_values for hardware interfaces when starting simulation.

[destogl]

This PR adds support for initial values to set the hardware's initial states in the simulation.

This functionality is based on the following ros2_control PR:

• Adding support for 'initial_value' parameter. ros2_control#593

Here is an example of its use in FakeHardware.

• Support of "initial_value" for the 'FakeSystem' ros2_control#598

The ros2_control changes are released but not yet synced.

[ahcorde]

DCO ?

[ahcorde]

Hi @destogl, I'm trying to compile this. Is initial_values feature only available in rolling ?

[destogl]

Hi @destogl, I'm trying to compile this. Is initial_values feature only available in rolling ?

Yes, this is rolling-only feature. I am not sure if it is synced already, but it is released.

[destogl]

DCO ?

Sorry about that!

[ahcorde]

Can you add the same example as you included in this PR here ?

[destogl]

Can you add the same example as you included in this PR here ?

Do you want to have two additional files for it? In this PR I embedded the example of initial_value into the existing one because we actually change only one line compared to the usual examples. TBH I rather prefer approach I done here. Otherwise we just add "file-noise" without much value in them.

If you insist to add an additional example, I'll add it, but as I said, I think it is overkill.

[destogl]

@ahcorde I think we can go on with this in the same way as had to be done for gazebo_ros2_control.

[ahcorde]

@destogl the PR is ready #30