v4.09.07 beta - Default I/O priorities now implemented

I went ahead and finished up the implementation of default I/O priorities in v4.09.07 beta. I did not add the configuration dialog yet, but context menu use is fine. I still do need to add them to the multi-selection process context menu as well.

Naturally, further beta builds are coming. I am VERY excited as v4.1 introduces some truly innovative features, of which this is just one. It further polishes up v4 final, fixing some minor bugs here and there. I would back-port some minor fixes, but it is hardly worth it since v4.1 will be here before we know it. It will also give people a break from updates.