Add new A0 size sheet class (and rename and hide the old one.)

A0 sheet size has bee wrong since SkyCAD existed.  Instead of being a 841mm x 1189mm as it should be, it has 1189mm x 1189mm.

The current A0 class will still exist so that existing projects using that class still work, but will be renamed to 'ISO A0 (Pre-version 1.3.44)' and hidden from an upgrade process.  A new 'ISO A0' class with proper dimension will be created in the same upgrade process.