* Put the parameters controls in a scrollable panel
* Fix InstructionSelectorDialog glitch when selecting an instruction
* Disable the horizontal scrollbar in InstructionsSelectorDialog
* Override parameter labels minimum size in InstructionSelectorDialog
so that they don't overflow from the scrollable area, hiding the parameters edition buttons
(also remove the horizontal scrollbar from the parameters scrollable area)
* Fix search text ctrl hidden by the tree ctrl in InstructionSelectorDialog
* Size fixes in InstructionSelectorDialog
* Fix unavailability warning msg displayed if an instruction has a custom generator
* Fix layout issues in ObjectsEditor and ChooseObject/VariableDialog