Add parser with type seed for creating tables with seed data

[medvedev1088]

For some parsers contract_address is a static list of addresses which is duplicated in other definitions https://github.com/blockchain-etl/ethereum-etl-airflow/pull/94/files#diff-f0b9ae4effce038c22ca6abf7dfec316R28.

Similar to dbt we can have a table definition with seed parser:

{
  "parser": {
    "type": "seed",
    "header": ["address"],
    "data": [['0xa'], ['0xb']]
  }
}

Then it can be used as a reference in other table definitions.