Change the sync label in vCard; introduce constants for vCard tags
return dumy True in bulk_clear_sync_tags, so del-profile method can be used from cmd line
Prevent the contact itemid from having // before the hash.
Fix error in parsing the carddav server uri which was preventing https uris from being mentioned
Properly expand user-dir if --user-dir option contains the ~ character
Restore BBDB backup(s) if if there is an exception during save

This fixes the issue described here: https://github.com/skarra/ASynK/issues/23

Basically, we resotre the last backup in case of failure.
A bit of refactoring has also happened in the course of this
Also enabled backups for hte clear_sync_flags operation
Document a corner case problem as FIXME comment
Support department, title, company fields synching from/to carddav.
Update dev log