Save selected service in instance settings

[lucasw]

This might help #2 also.

A restored rqt config/perspective ought to return to the saved service, even if it is not yet available (make it work like rqt_image_view a restored image topic will be appended to the list of live image topics, and then if the user selects another topic I'll have to check whether the restored topic is forgotten at that point).

Possibly a different issue and pr could also save and restore all the field data so the same service call could be ready to call without typing.

[Fruchtzwerg94]

I've created a pull request #3 solving exactly this issue about two weeks ago.
My pull request at rqt_image_view ros-visualization/rqt_image_view#13 was approved very fast by @dirk-thomas , I don't know why this request is still pending. Is there a problem with my implementation?

[dirk-thomas]

@lucasw The described behavior makes sense. Please consider providing a pull request for this enhancement. (If the service doesn't exist its type might not be available though. So I am not sure if this is possible...)

@Fruchtzwerg94 Your PR only select the previous service if it does exist in the combo box. This issue is about making it even add an entry if it doesn't yet exist in the list.