Changes:

Reworked save workflow to enable addition of layout syntax checker,
Added syntax check for each item in layout, warns if error is present,
Updated variables and comments in `write()`,
Fixed outdated comment for Save button,
Disabled New button (until code to support it can be written),
Added debug command-line parameter (`--debug`), moved debugging messages
under it,
Display complete error traceback to console if debug parameter is
enabled