Properly convert constants to CharType

Add macro to define enum/JSON mapping

Add BSON support

- added fuzz testers
- added some reference files
- made an exception text more clear

Merge branch 'feature/bson' of https://github.com/julian-becker/json into julian-becker-feature/bson

Allow to set error handler for decoding errors

Thanks @abolz!

Test every prefix of Unicode sequences against the different dump functions.

BSON: Improved exception-related tests and report location of U+0000 in the key-string as part of `out_of_range.409`-message

add new is_constructible_* traits used in from_json

Add Meson related info to README

Add more information about how one can get a Meson wrap file.
Signed-off-by: Kostiantyn Ponomarenko <konstantin.ponomarenko@gmail.com>

 Conflicts:
	include/nlohmann/detail/input/binary_reader.hpp
	single_include/nlohmann/json.hpp
	src/unit-bson.cpp

Improve diagnostic messages for binary formats

This commit is the equivalent of #1282 for CBOR, MessagePack, and UBJSON.