Extending the history

Extend the history
1. prepare for multiple undo's (collecting) [100% in Version 1.4.1]
2. multiple undo's [until version 2.0.0]
3. detection of already removed files.  [ ~ until version 2.0.0] 
      what to do then? how to report? if target file exists (keep copy or 
      replace? in batch?) ?
