* New fuzzy check logic:
- use shingles algorithm for fuzzy matching
- use blake2 instead of md5 for larger output space
- combine fuzzy and strict matching
- allow to organize private storages by means of keys
- preserve compatibility with previous versions
* New fuzzy storage:
- use sqlite instead of own memory based hash tables
- rework commands interface
- add conversion from the old format
- add fuzzy match by shignles
- support old rspamd versions
* Add lemmatizing for words used in fuzzy hashes that allows to improve match
quality by using of the first forms of all words
* Rework language detection
* Fix several critical bugs, memory leaks and deadlocks:
- memory leak in HTML nodes parsing
- deadlock in logger code
- deadlock in signals processing
- crashes in fuzzy_storage
- crashes in tokenizers if the input was empty
* Import new libucl with several bugfixes and improvements
* Support listening on ipv6 addresses only
* Fix macro expansion in SPF module
* Several bugfixes in DKIM module
* Add load headers support for mime parts to the lua API
* Add documentation for:
- workers in general
- fuzzy_storage worker
- fuzzy_check plugin
- mimepart and textpart lua API modules