#3 Auto Refresh Scheduling

[heretic108]

Create a timer thread class that waits till an
appointed time, then refreshes all sites.

At the appointed time, this thread must first check
that there are no refreshes already running. If so, it
should wait till these complete.

Once the appointed time has passed, and current
refreshes (if any) have finished, the timer thread
must tell the CSyncSite object to refresh all sites.