Add array support to JSON implementation

[tabularelf]

Been considering supporting this

{
    "greetings": [
        "Hi!",
        "Howdy!",
        "How do you do?"
    ]
}

---> "greetings0", "greetings1", "greetings2"

[tabularelf]

I might also provide a helper function that can pull out all of the entries that were fed from an array.
lexicon_entry_get_variations("greetings") --> ["greetings0", "greetings1", "greetings2"]
Will also work for entries that contain a struct within a struct with an array.

{
    "test": {
        "array": [
            "nice",
            "very nice"
        ]
    }
}

lexicon_entry_get_variations("test.array") --> ["test.array0", "test.array1", "test.array2"]