Include `base_config` dictionary for contact information in metacatalog `CONFIGFILE`

[AlexDo1]

The standards_export extension should update the CONFIGFILE (json) with the base_config for ISO 19115 export (contact and publisher).
At the moment, ISO 19115 information is extracted from CONFIGFILE in the following way, so we should use the top-level key extra with the sub-level key iso19115_contact:

base_config = config.get('extra', {}).get('iso19115_contact', {})

The dictionary in iso19115_contact could look like this:

dict(
    contact = dict(
        organisationName = 'METACATALOG',
        deliveryPoint = 'YOUR ADRESS',
        city = 'YOUR CITY',
        administrativeArea = 'YOUR STATE',
        postalCode = '12345',
        country = 'YOUR COUNTRY',
        electronicMailAddress = ['JANE.DOE@EMAIL.COM', 'JOHN.DOE@EMAIL.COM'],
        linkage = 'HTTPS://YOUR.URL.COM/',
        linkage_name = 'YOUR WEBSITE NAME',
        linkage_description = 'YOUR WEBSITE DESCRIPTION'
        ),
    publisher = dict(
        organisation_name = 'METACATALOG'
        ))