Introduce UTF-8 matcher construct in std.uni

The goal is to define functor that does
essential part of decoding and matching in the lockstep,
reaching higher performance.
use forcibly templated utfMatcher to keep inlining working
Add DDocs and extra primitive that consumes only on match
Version of UtfMatcher with UTF-8 decoding checks
try no-decoding
Tidy up code, prepare for generalization
Tidy-up and properly encapsulate Utf8Matcher
getting ready for submission - subMatchers, refactor the code
outline generic interface for both UTF-8/UTF-16
Flesh out UTF-16 Matcher

Fix an embarassing type in setSearcher.
Correct and finalize UTF-16 Matcher
Finalize DDocs and examples, accept plain strings
And add some UTF-16 in public examples
try to buy back some speed