Add Stop button functionality to RunEngineWidget and implement stop s…

[gnzng]

…ignal in QRunEngine

As mentioned in #39 this uses the stop() function of the RunEngine instead of abort(), which should mark it as a success.

[gnzng]

I tested it at the beam line and unfortunately it does not work exporting the files via bluesky exporter. I will dig a little deeper, when I find the time.

[ronpandolfi]

The finish state doesn't help that the files end up having less data than was anticipated. Databroker (at least in the version currently pinned) is probably failing by trying to read past the end of the data files.

I'm working on a big update of all xi-cam dependencies currently. Its possible that this behavior has been improved on in future databroker versions?

Nice work though! If we add a warning dialog to indicate this issue to the user I'd be happy to merge.

[gnzng]

Thanks for the feedback!
I just thought giving that a try first. I'll look into the databroker today and if a version update will fix that.

[gnzng]

Just to conclude some of the testing findings yesterday for future reference. When starting a single acquisition with many frames, and you are ok with the measurement so far and you would like to keep it: A workaround is to stop the acquisition directly on the detector server in the medm interface, instead of sending the stop to the RunEngine.