Fix status when the freshclam state file is empty
Initial bump for ClamAV::XS library

Thanks to @scabrero for doing it
Make deb packaging for ClamAV::XS
Fixing doc copyright
Small refactoring
Make FreshclamStatus model more resilient to errors

Use ClamAV::XS library to be more reliable and faster to count the number of signatures
Merge pull request #1024 from Zentyal/ejhernandez/fix-av-initial-steps

Fix several bugs when initialising zentyal-antivirus