Adding preliminary support for converting json schema to apache parquet schema.

[lvde21]

Related to issue: #2
Objective: hoping to get advice about approach.

Simple test:

EDIT: fixed a small bug in object field names.

$ aptos convert -format parquet tests/schema/person 
message ParquetSchema {
  optional group Person {
    required binary firstName (UTF8);
    optional binary lastName (UTF8);
    required int32 age;
    optional group Address {
      optional binary street_name (UTF8);
      optional int32 zipcode;
    }
  }
}