Fix updateAlarm failing when refreshTime is a string

refreshTime should never be stored as a string, but this fixes it when
it is.
Move settings from local storage to synced storage

Saved settings are automatically moved from storage.local to
storage.sync when any page loads shared.js.  It should probably be
removed in a later release after it has been long enough for the
function to have run for essentially all users.
Increase version number to 0.7