Validate SCDL catalogue

Follows #4 (closed)

• As I user,
• I want to use a SCDL catalogue as input,
• in order to validate all SCDL datasets at once.

Acceptation criteria

• Use generated catalogues of platforms (udata, ODS, CKAN, etc.)
• Infer the SCDL schema from the tags of resources

Information

• The SCDL catalogue is a dataset itself.