Clarify ROS default values will be used in default constructor

[dhood]

@mikaelarguedas explained this to me in ros-simulation/gazebo_ros_pkgs#793 (comment)

[mikaelarguedas]

I think there is still misunderstanding here.

In this article, "default value" always refers to the default value provided in the msg file.

We don't have the concept of "No default value at all" as we define default values for all the types we define in the ROS IDL format (detailed in this article)

[dhood]

since char wasn't listed in the article with common defaults I thought it was an example of the 'no default' category. I tried to clarify there's always a default in 93a6c39

[mikaelarguedas]

As this paragraph was duplicated below, is it possible to update the following lines as well ?

[dhood]

Other sentence updated in 77de52d

[mikaelarguedas]

lgtm.
Maybe @clalancette wants to review as he has the most context on this

[clalancette]

This clarification looks fine to me! I just corrected some spelling, otherwise, I think this is good to go.

[dhood]

thanks to you both!