Backwards compatibility is provided for vnd.dovecot.duplicate.
Still need to fix the constraint that it must not track duplicates from failed Sieve executions.

Some environment items in the base specification are not (yet) applicable to Dovecot and are therefore not supported.

Added support for the :optional tag of the include command.
Changed Sieve script API in the process; opening the script is now available as a separate step.

Additional paths are specified by adding a sequence number (starting at 2) to the setting name.
Added support for specifying home-relative paths for sieve_before and sieve_after.
This enables administrators to specify user-specific global Sieve scripts that cannot be viewed or changed by virtual users.

Old name is now deprecated.
Support for the even older global_script_path name for this setting is dropped.

ManageSieve: removed TODO status of adding ANONYMOUS SASL support, since the RFC specification no longer describes it.

Fixed README: now mentions the naming differences of the imap4flags and enotify extensions compared to the old CMU Sieve plugin.

Removed code duplication between testsuite and commandline tools. Also restructured source code of the tools.