digikamalbums ioslave:
- remove the old code for file operations that was copied from the file ioslave
- use KIO jobs to do file operations, enter an event loop, forward the result.

This is heavily inspired by ForwardingSlaveBase (read: copied from), but this class calls finished before we are finished and some other details, so we have again code copied from kdelibs (but not that much this time, and no low-level system API)