lib-sieve: file storage: Fixed bug that caused missing active symlink to cause a temporary error in some cases.

A conditional expression was inverted, causing the path to remain unnormalized.

Messed up the previous attempt.

The error status code wasn't set, so this was handled as an error rather than a warning in the LDA plugin.

lib-sieve: file storage: Improved backwards compatibility with respect to the active script being a regular file.

This is particularly important when the location is recorded in the binary for checking whether it is up-to-date.

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.

lib-sieve: Fixed bug in `:matches' match-type that made a pattern without wildcards match as if there were a '*' at the beginning.

This allows performing ManageSieve actions at command line or through doveadm server.

lib-sieve: file storage: Restructured storage initialization to address backwards compatibility issues.