support package format 3

[dirk-thomas]

As defined in REP 149.

[dirk-thomas]

In the current state it does successfully parse all manifest files of ROS 2, exposes an API for all new information as well as provide an API for condition evaluation.

It doesn't utilize the new information yet in any of the non-parsing API, e.g. consider group dependencies in topological order or passing context for the dependency conditions.

[dirk-thomas]

The patch now does utilize the new information in the topological order as well as uses the context to evaluate dependency conditions.

@ros-infrastructure/ros_team Ready for review.

[wjwwood]

I believe the pyparsing dependency needs to be added to the stdeb.cfg file too. Other than that lgtm.

I've mentioned this before, but I think it's worth repeating, as long as we're spending time on this, it would benefit us to consolidate the parsing code for package xml files.

[dirk-thomas]

I believe the pyparsing dependency needs to be added to the stdeb.cfg file too.

Thank you - good catch. I added it here.

[dirk-thomas]

Waiting for a confirmation from @nuclearsandwich before merging...

[nuclearsandwich]

This PR allows bloom to release ROS 2 packages that use format 3 manifests.