collect: bugfix to not symlink yourself

* Removing the destination folder from the list of folder to read from.
  The destination folder is also the application static_folder so it be
  unset before running the collect operation. (fixes #244)

* Ignoring the existing files in the output log of the command and
  showing only the one added, with a nice counter at the end.

Signed-off-by: Yoan Blanc <yoan.blanc@cern.ch>
Reported-by: Jan Åge Lavik <jan.age.lavik@cern.ch>