JSONToTable converts vector-like strings even with ignoreConversions

In #lua-help, 0d9b reported that util.JSONToTable turns strings that look like vectors into vectors even when called with ignoreConversions set to true. He asked whether this is intended, calling a JSON parser that mangles the output without an option to keep the original values "a bit useless for... parsing json". Artemking4 said he prefers MessagePack.