New message definition for the ToolData

[NikolasE]

This PR contains a new message definition for the ToolData that contains the analog inputs from the tool which where not available so far. The message contains numerical constants so that the user can understand the flags and modes easier.

[gavanderhoorn]

ROS naming conventions: the V should be lower case.

[NikolasE]

fixed

[NikolasE]

@gavanderhoorn: Could you approve the PR? I could then open a PR to integrate the related parsing code into the ur_modern_driver

[gavanderhoorn]

I think the comment should read: # one of TOOL_*?

[NikolasE]

fixed

[gavanderhoorn]

A comment on this PR: thinking about it a bit, I'm actually not really a fan of adding these kind of messages. I'm rather a fan of having ROS drivers publish messages that are interpretable on their own, instead of needing another bit of information to be able to understand their contents.

In this case, I'd rather the ur_driver / ur_modern_driver publish values for the analogue inputs / outputs that are already converted (using the data in the ToolData packet in the binary stream coming from the controller). That way we don't shift the responsibility of doing that to consumers of the data.

I'll still merge it, but I think we should take a good look at how we want to handle these kind of cases in the future.

[gavanderhoorn]

@ThomasTimm: fyi.

[gavanderhoorn]

@NikolasE: I've had to update your indigo-devel branch to merge in some commits from #275.

If you have the time (and opportunity), it would be nice if we could squash all your commits into one, and do a rebase on top of current indigo-devel. That would avoid the merge commit as well.

[gavanderhoorn]

@NikolasE: ignore my last comment.

I've squashed your commits and merged them in b26b61d.

Thanks for the PR.