Support for renaming fields

[Fryuni]

Avro schema evolution supports field renaming by setting the old name as an alias of the new name on the new schema.

If a field is missing on BigQuery is missing from the schema but is an alias to some other field, currently, this causes an impossible update, but there is no need to update the table schema since this is a backward-compatible schema evolution for Avro.

This issue was previously reported on the original repo at the wepay#293