cleanup #663

[rhaschke]

This PR provides some cleanup to the previously merged PR #663.
As a major regression, after #663, displaying of attached collision objects didn't work anymore (#723).
Besides fixing this, the present PR provides some other minor improvements.

[v4hn]

I don't see the need to break (released) API just because it's redundant.
But I do approve the change set as is.

@rhaschke @jeffreyling sorry for the simple oversight...

[v4hn]

Tests for the PlanningScene #667 would have helped, but nobody got around to review this yet.
Not to mention adding a test for this case.

I'll merge this to fix the bug and remove the release blocker.

[rhaschke]

@velveteenrobot As we had a regression after accepting your original PR #663, may I ask you to provide some unittests that validate the API to interact with the planning scene? This will help to avoid regression issues in future.
For example, you could insert collision objects through various API calls and validate that your new getters will fetch the correct messages. Thanks a lot in advance.

[velveteenrobot]

I probably won't get around to this for like a month but if no one beats me to it, I should be able to put in some unit tests in January.

[rhaschke]

Thanks. That would be great.