actually allow underscore in labels

commit 756410d forgot a character
refactor the whole label business
Hooks up LEM1802 to demo page.

- Replaces tabs with spaces in index.html

- Fixes some issues with hooking onto CPU memory setting events in
  LEM1802 device.

- Replaces simple display in index.html with canvas + LEM1802.

- Changes demo program assembly to use LEM1802.