Add database creation to MySQL.

Schema creation is supported using a file. The provisioning script
checks if the database exists before attempting to create it, so
multiple runs are ok (considering the SQL file is also able to be
executed multiple times).
Move MySQL database creayion to helper script.

Previously a separated script, it is now on a helper script which is
used by MySQL and MariaDB scripts in order to enable remote access and
create/import databases.
Merge branch 'mysql-import-database'