Refactor a little for less work and code:
  Only form a file page and make a QImage and QPixMap
  when the cursor moves to a different page, not every
  time the zoom changes. Also move the conversion to
  png8 into the load instead of repeating it in
  zoom-to-width and -to-height.
Major logic rewrite to clarify state changes, and
to minimize the amount of work done when cursor position changes.
Changed pqNotes to use the prepared page number instead
of formatting its own. Then removed unused IMC element.
Correct page number class name to pagenum to match guiguts and the pg wiki