diff per backend
  * intext and side-by-side diff
  * revert single changes from ui
remove notifications in the ui after 10sec
breakout side-by-side-diff from the container in the ui
  * container too small for a side-by-side diff
move css into zsd.css
fix check if file has changed when md5 is used
  * only individual snapshots where compared
  * if a file was restored, 'FilterWhereFileWasModified' was incorrect
    - it has versions listed with the same content as the actual file
  * now the actual file md5 a compared too
new compare-file-method: auto
  * use md5 on text files
  * size+modTime on others
  * is the new default
update README