fixed bug where maildirs that start with a number were skipped. make deleted maildirs record the date they were deleted

find: warning: you have specified the -maxdepth option after a
non-option argument -type, but options are not positional (-maxdepth
affects tests specified before it as well as those specified after
it).  Please specify options before other arguments.

 - general cleanup of dup handler
 - support remove-older-than command
 - also run "duplicity cleanup" before anything else, for safety reasons
 - migrated full/incremental backup switch to new syntax
ChangeLog: removed trailing space