Tried to get keyboard to show up but it don/t
Fixed some annoying bugs:
- Registered the main activity as a preferences listener so we can
automatically reinitialze all the important objects when the spreadsheet
is changed. Verified that I can change spreadsheets and make changes.
Had to fix a bug where the old updater thread would keep running.
- This should also help things in the initial state where no spreadsheet
has been chosen. Now the display should be disabled. PLUS, you should be
able to back out and do nothing, and then select a spreadsheet and have
it all work.

Have not yet verified start-up behavior.