Need code cleanup: ArchiveLoadAsync

[fire-eggs]

The quick-and-dirty load of "archive containing archives" has made the code a bit too much of a cobble.

1. Have lost "async" feature: containing archive has to be fully extracted before any image shown
2. Too much duplicated code.
3. 'activeFileNames' cobble.
4. Passing too many parameters for ExtractFile.
5. Possibly leaving temp files around (not deleted)