Add ArchiveIterator
Fix RARchive.OperationProgress

OperationProgress was not being raised; that code was removed along with
the old RARchive processing code
Add ArchiveIterator.Reset and Close methods
fix demo progress bar off-by-one error
Fix ExtractItem mode
Remove duplicate call to OperationProgress
ArchiveIterator.Rest now returns immediately if the handle is invalid
Add UnRar.IterateArchive method
Fix RARHeaderDataEx structure and RARItem
Merge pull request #1 from charonn0/ArchiveIterator

Introducing the ArchiveIterator class