Update Imperial Onslaught quest drops (#1122)

This is the start of the work to replace the existing 50-of-everything
drop tables with hand-picked values.

For these drops I've used the clears helpfully uploaded here
https://www.youtube.com/watch?v=PBA7tQtd5Kw as a reference, with some
fudging to round numbers since we are supplying averages.

Also a minor visual fix for every drop having a 'New!' adornment on the
drops screen