QIF importer improvements

[Charles Day]

I've committed a pretty large set of changes for the QIF importer in r17245
which integrates a progress page into the druid with pause, cancel, and
error logging during the loading and parsing phases. This replaces one of
the pop-up progress bars that was being used. There has also been a variety
of improvements and additions to error and warning messages. So there is
definitely some new work for translators to have a look at.

I've tested this until I'm bleary-eyed, and it all seems to work great, but
if anyone else wants to play with it and try to break it, so much the
better. You'll need to test with a fairly large QIF file if you want to play
with pause and cancel. I did spot one small mistake which has already been
corrected in r17246.

Cheers,
Charles