Initial experiments for the US Qwerty layout
Make layout configurable

Make layout configurable and provide 4 default layouts: left- and
right-handed US Qwerty and left- right-handed Canadian French.
Reorganize the code, add mappings
Remove dead code
Better variable names
Move some code into a function
Move again some code into a function
Simplify the code
Move a comment to a better place
Comment formatting