Realtime Publisher - Select one behavior (Polling or NonPolling) and remove the other one

[firesurfer]

I just refactored the RealtimePublisher in #211 and I am wondering if we really need these two different behaviors of the RT publisher.

They make the code harder to read and maintain. In accordance with #199 I would suggest to use the non polling behavior and remove the other one.

Perhaps someone could point out a use case where one or the other is preferable?

[firesurfer]

Only place in ros-controls the NON_POLLING define is set is in the tests of this repository:

https://github.com/search?q=org%3Aros-controls%20NON_POLLING&type=code

If I search more general I can only find it in this repo and forks of it
https://github.com/search?q=+NON_POLLING+AND+realtime_tools&type=code

[bmagyar]

Sorry for being late on this, @christophfroehlich has brought this to the Working Group meeting.

I also agree that we should strive for using non-polling everywhere, especially now that it can be implemented in an elegant and transparent way.