uORB Messaging - Docs on new interface

[hamishwillee]

As discussed here there is a new uORB interface. Should result in docs update to uORB Messaging · PX4 Developer Guide. Assigning to @dagar to at least kick it off.

@bkueng Do you know of any other places that need to be updated?
Not knowing anything about the changes, the things that spring to mind are First module doc and the Module template. If needed, could you sort out those changes?

[dagar]

It seems we don't actually have much specific documentation in the first place.

For one thing the troubleshooting and common pitfalls no longer apply.
http://dev.px4.io/master/en/middleware/uorb.html#troubleshooting-and-common-pitfalls

Updating the module template and an example might be the next step.

[hamishwillee]

Thanks. I deleted the troubleshooting/common pitfalls section.

@bkueng Can you update the module template/example?