lib-sieve: vnd.dovecot.report extension: Added support for configuring the "From:" address used in the report.

A "vnd.dovecot.config.<identifier>" environment item maps to the content of the matching sieve_env_<identifier> plugin setting.

lib-sieve: vacation extension: The sieve_user_email setting is now used in check for implicit delivery.

This means that vacation responses are now also sent for messages that include the sieve_user_email address in one of the relevant headers.

The recipient_delimiter is treated as multiple one-character delimiters
rather than one multi-character delimiter if more than one character is
supplied.

Based on a patch by: Lennart Weller <lhw@ring0.de>

This is used mainly when no other means of obtaining the user's email is available, such as when there is no envelope (in IMAP).
Before, the postmaster address or the null "<>" address was used as a fallback for sending messages.
The redirect and enotify commands can be explicitly configured to use what is configured with sieve_user_email.

It allows sending feedback report (RFC 5965) messages.

lib-sieve: multiscript: Fixed bug in handling of (implicit) keep; final keep action was executed as though there was a failure.
Among other things, this caused the keep action to revert back to the initial message, causing editheader actions to be ignored.

lib-sieve: mime extension: Fixed the header :mime :anychild test to work properly outside a foreverypart loop.

test suite: mime extension: Improved header test cases to catch header trimming and folding problems.

lib-sieve: message body: Fixed assert failure occurring when text extraction is attempted on a empty or broken text part.

Included scripts now execute in the context of the inner parent foreverypart loop.

An empty string yielded an empty string rather than "0".

It now extracts bare text from HTML/XHMTL parts.
Other text/* parts are still returned as is. Any other unrecognized content types are skipped.

This allows setting the MAIL FROM of the SMTP envelope for the notification e-mails.
The syntax is identical to the sieve_redirect_envelope_from setting.

lib-sieve: editheader extension: Made protection against addition and deletion of headers configurable separately.
Also, the received and auto-submitted headers are now only protected against deletion as required in the RFC.
Updated the documentation accordingly.

Currently cannot freely assing server metadata items for testing.
Disabled tests for now.

Also added testsuite items to test syntax.

Based on patch by Timo Sirainen.

Doveadm-sieve plugin may be broken at this point; not tested so far.