API improvements in the recently added FileUndoManager (capitalization of enum, helper method)

Had to add accessor to CopyJob for the type of operation (copy, move, link)

Fixed nasty crash in CopyJob triggered very indirectly by FileUndoManager::recordCopyJob: when the KUrl::List srcUrl parameter was detached, the stored iterator would then become invalid and crash, fixed by using a const iterator and constBegin/constEnd.