Fix bug: comma key ignored when useCommaKey=false

With useCommaKey=false the input would ignore the comma key making it impossible to refine the data lookup for values with commas in the text.

Fix includes:
- changed the _onKeyDown function case statement to look for Tab 9, Esc 27, Enter 13. It was looking for 188 as Esc.
- refactored hard coded keycode values into a lookup variable KEYCODES