DOS Quick Reference Card - Remake

Hi,

in the same spirit as for the "Applesoft II Basic Quick Reference Guide", I've also finished recreating the "DOS Quick Reference Card". All typos and any other small issues in the original document have been preserved to look exactly like the original.

The document(s) now have their own Github repository at: https://github.com/egrath/apple-quickrefs

Hope that someone could make use of the document.

With kind regards,

Egon