Release 1.5.6

Release 1.5.6

* [Feature] Add unigramms support in bayes
* [Feature] Allow configurable sign headers for DKIM
* [Feature] Allow to add unigramm metatokens from Lua
* [Feature] DKIM Signing: envelope match exception for local IPs
* [Feature] UCL: register parser variables from Lua
* [Fix] Always try to adjust filename
* [Fix] Do extra copy to ensure that original content is never touched
* [Fix] Fix SPOOF_REPLYTO rule
* [Fix] Ignore Rmilter added Received
* [Fix] More fixes for hashed email dnsbls
* [Fix] Plug memory leak in chartable module
* [WebUI] Display multiple alerts at once

Signed-off-by: Vsevolod Stakhov <vsevolod@highsecure.ru>