add options for very large market lists

[jbmccune]

I have 30K+ items listed on the market, and though this tool is awesome for dealing with that much data when I need to perform operations across those many pages, loading all of that data every time kills me when all I want to do is clean out orphaned pending confirmations. I hacked the code to stop after 100 items for now, but some options to only process the first page, or only so many items, or just to hide the listings and not process them at all, until a button is clicked (to either load more or the rest) would be awesome.

Also, given how long it takes to load pricing information for so many items, it would be nice to have some visual indication of progress, so I know when it's done and I can start performing price-related operations without having to go to the last page to check. Similarly, it would be nice to have some indication of progress for long, multi-page operations like removals or relisting - "10/1000 processed" or something.