- Add filter support
   * filter
- add source/ignore_failed_pre_exec
- add source/ignore_failed_post_exec
- do not delete_incomplete, when there's only one backup left!
- .ccollect-marker is deleted by rsync at the beginning!
   - fix marking
- add logwrapper
- add loganalyser
   speedup is
   error codes
   vanished files (see netstream)!!!

Done:
- Improve finding backup from another interval:
   o strip of interval name
   o run sort -n
   o use the last entry
- add --version, -V

not needed:
- think about 'prefer_same_interval' / 'prefer_latest'

