DO12 - Synchronize improvements

As with multi-file (multi-part/threaded) FTP support, I was also hoping for multi-threaded scan/compare during Synchronize operation. Some backup software I use does multi-threaded compare and it's much faster. This should be easier to implement than multi-file/part FTP, since the existing progress GUI can be used - it's just that the progress of each thread needs to be combined into total progress figure.

I know Jon's said in the past that Opus is never going to be as good as specialist tools for specific tasks, but what I'm asking for is a refinement/optimization of what is already there, rather than a whole load of new features for these tools.

A little bit of info re. multi-threaded scanning...

bvckup2.com/wip/27122012