支持集合属性

目前很多的newsql都支持集合属性，对应datax core比较简单，增加
public class CollectionColumn extends Column
public enum Type {
BAD, NULL, INT, LONG, DOUBLE, STRING, BOOL, DATE, BYTES, COLLECTION // MAP
}

Start in DataX core by reading the existing Column model and the surrounding data-type handling. Determine how a generic CollectionColumn and the proposed COLLECTION type would integrate with current readers and writers; done means collection-valued attributes are represented consistently without breaking existing types.

Written by the indexing model from the issue text.