MDL-41669 Restore: Progress bar needs to include more tasks

1. Changes progress bar code to allow headings for progress bar (so users have
   some clue what's going on if a page has more than one progress bar).
2. Changes restore code so that a progress bar can display during pre-checks if
   they take longer than 5 seconds.
3. Changes pre-check and restore code so that, in various points where the system
   can take a long time within an individual step, intederminate progress is
   indicated and it won't time out.