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Features:
* config: config_format=2 switches to extended format.
* querybuilder: alt SQL for missing value.
* querybuilder: handle more value types in inline queries.
* querybuilder/plpy: always use prepared plan. Prevously when GD/SD
was not given, it switched to inline params, but that was problem
because inline value quoting may be different that PL/Python's.
Now it always uses plpy.prepare.
Cleanups:
* querybuilder: switch to functools.lru_cache, instead local LRU.
* querybuilder: use regex for parsing, gives cleaner code.
* querybuilder: improve error handling
* natsort: switch to string key, instead of tuple.
* style: Add type annotations to most modules.
* style: use new-style super() everywhere.
* ci: drop win32 repack, abi3 is now supported on win32
* ci: drop ubuntu 16.04, to be obsoleted.
* ci: build wheels using manylinux2014 images.