Support MySQL & PostgreSQL stores

[moshest]

This PR will add support for MySQL and PostgreSQL via the SQLStore.

In this PR we will add 3 more packages:

• @neuledge/sql-store - general SQL store with an abstract connection
• @neuledge/mysql-store - a MySQL store based on mysql client
• @neuledge/postgresql-store - a PostgreSQL store based on pg client

Track of implemented store methods:

• [x] listCollections()
• [x] describeCollection()
• [x] ensureCollection()
• [x] dropCollection()
• [x] find()
• [x] insert()
• [x] update()
• [x] delete()