More simplifications for SampleDesigner Toolbox

See merge request !245

copied from Qt source and modified according to our needs

* make Qt connections compile-time-safe (do not use SIGNAL/SLOT macros)
* rename "category" to the more appropriate "group", to eliminate QtDesigner residuals

"WidgetBox" was due to widget selection in QtDesigner, from which this class was copied once

Prepare for ISimulation w/o Instrument

See merge request !242

Rename classes and fcts in context of polarization

See merge request !244

Rectify install command for qAccordion

See merge request !243

fix broken debug compilation (in context of handling windows warning LNK4098)

See merge request !241

Prepare for ISimulation w/o Instrument

See merge request !242