BibTasklets: various fixes for consyn

* Adds 2 new execution modes to exctract and convert
  files from a zip package or a list of packages.

* Appends a message with the summary of the harvest
  on the end of the bibsched log.

* Reports a summary of the harvest to the desired
  receipient (CFG_CONSYNHARVEST_EMAIL).

* Fixes imports.

* Updates the task to automatically delete
  the CONSYN atom feed file from disk.

Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>