Update dovecot2 to 2.2.28, and bump PORTREVISION on the plugins.

• director: "doveadm director move" to same host now refreshes user's timeout. This allows keeping user constantly in the same backend by just periodically moving the user there.
• When new mailbox is created, use initially INBOX's dovecot.index.cache caching decisions.
• Expunging mails writes GUID to dovecot.index.log now only if the GUID is quickly available from index/cache.
• pop3c: Increase timeout for PASS command to 5 minutes.
• Mail access errors are no longer ignored when searching or sorting. With IMAP the untagged SEARCH/SORT reply is still sent the same as before, but NO reply is returned instead of OK.
  
  + Make dovecot.list.index's filename configurable. This is needed when there are multiple namespaces pointing to the same mail root (e.g. lazy_expunge namespace for mdbox). + Add size.virtual to dovecot.index when folder vsizes are accessed (e.g. quota=count). This is mainly a workaround to avoid slow quota recalculation performance when message sizes get lost from dovecot.index.cache due to corruption or some other reason. + auth: Support OAUTHBEARER and XOAUTH2 mechanisms. Also support them in lib-dsasl for client side. + auth: Support filtering by SASL mechanism: passdb { mechanisms } + Shrink the mail processes' memory usage by not storing settings duplicated unnecessarily many times. + imap: Add imap_fetch_failure setting to control what happens when FETCH fails for some mails (see example-config). + imap: Include info about last command in disconnection log line. + imap: Created new SEARCH=X-MIMEPART extension. It's currently not advertised by default, since it's not fully implemented. + fts-solr: Add support for basic authentication. + Cassandra: Support automatically retrying failed queries if execution_retry_interval and execution_retry_times are set. + doveadm: Added "mailbox path" command. + mail_log plugin: If plugin { mail_log_cached_only=yes }, log the wanted fields only if it doesn't require opening the email. + mail_vsize_bg_after_count setting added (see example-config). + mail_sort_max_read_count setting added (see example-config). + pop3c: Added pop3c_features=no-pipelining setting to prevent using PIPELINING extension even though it's advertised.
• Index files: day_first_uid wasn't updated correctly since v2.2.26. This caused dovecot.index.cache to be non-optimal.
• imap: SEARCH/SORT may have assert-crashed in client_check_command_hangs
• imap: FETCH X-MAILBOX may have assert-crashed in virtual mailboxes.
• imap: Running time in tagged command reply was often wrongly 0.
• search: Using NOT n:* or NOT UID n:* wasn't handled correctly
• director: doveadm director kick was broken
• director: Fix crash when using director_flush_socket
• director: Fix some bugs when moving users between backends
• imapc: Various error handling fixes and improvements
• master: doveadm process status output had a lot of duplicates.
• autoexpunge: If mailbox's rename timestamp is newer than mail's save-timestamp, use it instead. This is useful when autoexpunging e.g. Trash/* and an entire mailbox is deleted by renaming it under Trash to prevent it from being autoexpunged too early.
• autoexpunge: Multiple processes may have been trying to expunge the same mails simultaneously. This was problematic especially with lazy_expunge plugin.
• auth: %{passdb:*} was empty in auth-worker processes
• auth-policy: hashed_password was always sent empty.
• dict-sql: Merge multiple UPDATEs to a single statement if possible.
• fts-solr: Escape {} chars when sending queries
• fts: fts_autoindex_exclude = \Special-use caused crashes
• doveadm-server: Fix leaks and other problems when process is reused for multiple requests (service_count != 1)
• sdbox: Fix assert-crash on mailbox create race
• lda/lmtp: deliver_log_format values weren't entirely correct if Sieve was used. especially %{storage_id} was broken.
• lmtp_user_concurrency_limit didn't work if userdb changed username