Generic field editor

[paoloambrosio]

We need a more generic control to edit fields, to avoid having to hardcode form fields in the view. File operations will stay the same.

Notes:

• The DataGrid control seems to be better suited than a form
  • It can be editable (see Editable datagrid? AvaloniaUI/Avalonia#8210)
  • It can be grouped (see DataGrid with groups? AvaloniaUI/Avalonia#6612) to reflect sub-groupings in files (e.g. engine section of chassis file)
• There are a few other data-driven repeating controls