Added DOxygen-style doctrings to most functions and methods #740

Job	Run time
windows-msvc-shared (UBJSON)	6m 55s
windows-msvc-shared (PARQUET)	36m 7s
windows-msvc-shared (CAPNPROTO)	8m 17s
windows-msvc-shared (JSON)	10m 55s
windows-msvc-shared (XML)	3m 51s
windows-msvc-shared (YAML)	4m 27s
windows-msvc-shared (CBOR)	7m 59s
windows-msvc-shared (AVRO)	6m 52s
windows-msvc-shared (BOOST_SERIALIZATION)	6m 27s
windows-msvc-shared (MSGPACK)	3m 45s
windows-msvc-shared (TOML)	4m 8s
windows-msvc-shared (FLEXBUFFERS)	6m 12s
windows-msvc (BOOST_SERIALIZATION)	25s
windows-msvc (CAPNPROTO)	25s
windows-msvc (CEREAL)	25s
windows-msvc (JSON)	25s
windows-msvc (CBOR)	25s
windows-msvc (UBJSON)	25s
windows-msvc (MSGPACK)	25s
windows-msvc (AVRO)	25s
windows-msvc (PARQUET)	25s
windows-msvc (XML)	25s
windows-msvc (TOML)	25s
windows-msvc (YAML)	25s
windows-msvc (benchmarks)	25s
windows-msvc (FLEXBUFFERS)	25s
	1h 51m 45s

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