- The commanding lambda now correctly receives a constant index and
  therefore the correct tab name is changed.
- When previewing an INI file where all that has been done was to open
  an application without changing anything, it is now still marked as
  unsaved (because although it might save a click in special situations
  it does not make sense to have a different logic than in the GUI and
  can only be confusing).
- Default names now get an .ini file extension i. e. unsaved(1).ini.
- Path/filename splitting is done once on file changes and then reused
  from outside without asterisk shuffling.
- Minor logic cleanup, consts and styling