Simplified/reorganized  update logic

Previously, we'd see if it was time to generate an update by setting a
boolean `doUpdate`, and just before checking that, setting it to be true if we
were forcing an update. Got rid of those two lines of code by changing the
test to

if doUpdate or self.force:
Moved the Settings class into its own file, renamed.

Changed from Settings to JsonSettings, in file jsonSettings.py