oof.py: Format code to meet PEP8 style guide
oof.py: Fix wrong variable name
oof.py: Ensure files are closed if exceptions are raised
oof.py: Make out of office independant from Zentyal

There is a new section and two new config keys for ocsmanager.ini to set
the sieve script path for the mailbox and to create the required directory
hierarchy if it does not exists.
Merge pull request #85 from Zentyal/scabrero/oof-zentyal-independant

Scabrero/oof zentyal independant