Add unit test to verify support for arrays in AvroScheme

[kkrugler]

From Sowmitra on May 19, 2015:

Finally zeroed in on the problem. For one of the datasets, I was using AvroScheme instead of PackedAvroScheme, and the data I was reading had a schema like below. Looks like AvroScheme does not handle the ser/de of the array field well. Are you aware of any issues around that?

The schema he was using looks like:

{
    "type" : "record",
    "name" : "Object",
    "fields" : [ {
        "name" : "field1",
        "type" : "int"
    }, {
        "name" : "field2",
        "type" : "string"
    }, {
        "name" : "field3",
        "type" : "boolean"
    }, {
        "name" : "field4",
        "type" : {
            "type" : "array",
            "items" : {
                "type" : "record",
                "name" : "field4_type",
                "fields" : [ {
                    "name" : "subField1",
                    "type" : "string"
                }, {
                    "name" : "subField2",
                    "type" : "string"
                } ]
            }
        }
    } ]
}