Define more keys

Defined some more keys in the calculator.  Started moving them into a
logical order in the file.
Code to generate printable format numbers

The code to manipulate the numbers into a printable form for the
output display.
Added new file

Added the display.lisp file to the project.
Added a new macro for key functions

Added a function to round off a number to a displayed precision.
Support for display modes

Added display width and floating-point representation modes.