Improve query efficiency and improve feedback to user
This change adds a check for the highest synced changed. Instead of blindly
running sync over and over Pulse now runs ‘p4 changes -m 1 //<client>/...' and
if the number is higher than the stored value it runs sync and then stores the
new highest change. Highest change numbers are written to the preferences to
further reduce needless queries.
With this change we also fetch the list of changes between the previous high
change and the new one so that we can report the number of changes synced.