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

Change backported from Pigeonhole v0.4 tree, which means that this change will duplicate there upon merge.

sieve-refilter: improved man page documentation by explicitly specifying the syntax used for mailbox arguments.

- Now compiles regularly without --with-unfinished-features
- Still experimental though, so be careful.
- Changed command structure a bit, removing the useless -M option.

Made vnd.dovecot.debug extension available to the LDA plugin instead of only the command line tools.

- No longer track the generated pigeonhole.7
- Some makes don't like the 'handy' notation that was used.
- Deleted trailing spaces
- Escaped some dashes
- Replaced some ' and " by \(aq and \(dq
- Sorted manual pages in section 'See also'
  (first list all man pages from the lowest section (1)
  alphabetical sorted, then the next section …)