Added DOxygen-style doctrings to most functions and methods #734

Job	Run time
windows-msvc-shared (JSON)	10m 53s
windows-msvc-shared (XML)	4m 7s
windows-msvc-shared (CBOR)	7m 31s
windows-msvc-shared (CAPNPROTO)	8m 11s
windows-msvc-shared (FLEXBUFFERS)	5m 59s
windows-msvc-shared (UBJSON)	7m 30s
windows-msvc-shared (YAML)	4m 30s
windows-msvc-shared (TOML)	3m 56s
windows-msvc-shared (BOOST_SERIALIZATION)	7m 22s
windows-msvc-shared (MSGPACK)	4m 31s
windows-msvc-shared (AVRO)	7m 56s
windows-msvc-shared (PARQUET)	38m 59s
windows-msvc (AVRO)	5s
windows-msvc (JSON)	5s
windows-msvc (benchmarks)	5s
windows-msvc (CAPNPROTO)	5s
windows-msvc (FLEXBUFFERS)	5s
windows-msvc (XML)	5s
windows-msvc (CBOR)	5s
windows-msvc (YAML)	5s
windows-msvc (PARQUET)	5s
windows-msvc (BOOST_SERIALIZATION)	5s
windows-msvc (MSGPACK)	5s
windows-msvc (UBJSON)	5s
windows-msvc (TOML)	5s
windows-msvc (CEREAL)	5s
	1h 52m 35s

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