fix for mysql 8.0 database

[Draed]

the Alpine MySQL client package (assembled from MariaDB sources) is incomplete and is not compatible with a default MySQL 8.x install :

• Adding 'mariadb-connector-c-dev' package.
• Update docker pip package version to 6.1 as 4.1 return error : request() got an unexpected keyword argument 'chunked'.

[einarf]

Thanks. I had to resolve some new issues caused by these changes, See commit log.

[einarf]

0.7.0 should be out