MySQL data source plugin

[evgenyigumnov]

1. Implement from_mysql function

// this function return string with json data like in report-data.json file
fn from_mysql(connection_url: &str, table_name: &str, columns_name: &[&str]) -> Result<String, ReportError> {
    todo!()
}

63cfa42

https://github.com/igumnoff/metatron/blob/main/data/report-data.json

2. Units test requered for this new feature