Review/refactor slots and other methods

[uliska]

It seems that many things are not at their proper place yet. While this doesn't affect the functionality I would prefer making the architecture right before the initial release as much as possible.

To be considered are the questions

• What action/slot/method belongs to Panel/Widget/View?
• What belongs to the base class and what to the child class?

I have already done a few things but held them back due to the massive working on the session handling. So I will start by re-applying these things and then have a look.

[uliska]

I think I'm through with the panel and the widget classes. What remains to be done (now or later) is the whole DocumentChooserAction complex. But maybe this one has to be reconsidered anyway.

[uliska]

I have now (as of c474727) moved everything from the manuscript viewer's document chooser action to the base class.
.

[uliska]

@PeterBjuhr I think this can be closed now