RCMCardDAV v5.1.0

• Allow to hide contacts without email also for user-defined addressbooks (Fixes #429)
• Re-introduced option preemptive_basic_auth to send HTTP basic Authorization header with every request. Also settable via user-interface. (Fixes #407)
• Support setting roundcube's default addressbook to an addressbook from a preset (Fixes #440)
• New option ssl_noverify to disable verification of the CardDAV server`s SSL certificate in HTTPS connections. Also settable via user-interface.