Everything in its place

With this release, I have moved all the code for each key to a procedure and removed it from the case statement that dispatches according to key code. This will let the user rearrange the keyboard to their liking and allow the key procedures to be used in later key procedures.
This is a pre-release but it is also fully usable for the procedures provided so far - which is a minimum viable set.
Discus and comment at https://www.reddit.com/r/pascal/comments/k1jgok/introducing_calcula_a_visible_scientific_rpn/

minimum viable product

Still needs a lot of work, and some features still need to be added - summations clear/summation add/ summation remove. arc trig and possibly hyper trig functions and perhaps even factorial.