Support MySQL & PostgreSQL

[dcolley]

I ported polka-store to sequelize.org so you can have other SQL databases. Supported Databases:

• MySQL
• MariaDB
• SQLite
• PostgreSQL
• Redshift
• MSSQL
• Snowflake (Experiment)
• Oracle Database

Let me know if you want to merge this and I'll create a PR.

https://github.com/metaspan/polka-store

[kevin-hermeneutic]

Hello dcolley, I was wondering if you have indexed data polka-store for polkadot chain from genesis block(0th) to the current block(17.2million blocks)?