Add database schema to GitHub

[maximmasiutin]

Could you please consider adding database schema to GitHub, i.e. SQL statements that create all tables used by PetScan, i.e.:

CREATE TABLE started_queries (
    querystring VARCHAR(4095) NOT NULL,
    created VARCHAR(255) NOT NULL,
    process_id BIGINT NOT NULL,
    id BIGINT NOT NULL AUTO_INCREMENT,
    PRIMARY KEY(id)
);