Ability to grant access to more than 1 database

[mikesimons]

At present the only way to grant perms is with the database_name parameter to the mysql_database_user provider.

This parameter does not support multiple values, therefore it is only possible to grant a user access to one database.

This either needs expanding to support multiple database names or an additional grants section of the config needs creating. This can map on to the mysql_database_user provider with action :grant