Transformation widget: update pixel size value and interface

TODO

• modify values from ID06 setup to ID03 setup (close #121 (closed) ).
• quick refactoring to improve user-friendliness and expose used values.
• Add the _MagnificationFactorWidget widget. That might be useful for #91

warning

• !312 (merged) needs to be merge first
• this does not 'ewoksify' the widget. This will be done in another PR

GUI

previous GUI

updated GUI