* If the export doesn't need buffers, we export directly from the loaded
capture file instead of re-loading it.
* Add progress bars for the load step so it shows what's happening
instead of looking stalled.
* Reduce compression rate on XML+ZIP buffers as it took too long trying
to compress when exporting large captures.
* Mostly used for passing a progress float back during a long blocking
call like opening a capture or doing a copy.
* This is much more feasible for python to bind to.
* In several cases we just use a tiny lambda that updates a float anyway
since we can't push the progress directly into a progress dialog, but
need to let it query from a temporary in-between float.
baldurk