Starting the integration process slowly on github

Dear all,

This mail is just to inform you that I am starting a slow integration
process of old SSN, new SSN, SOSA in a single folder on github.

see branch maxime-ssn and pull request:
 - https://github.com/w3c/sdw/pull/536

I will try to decompose the commits, raise issues, wait for consensus.

The first round consists in checking the methodology, the ontology
declarations, the server requirements, and the ontology metadata.

See among other issues:
 - https://github.com/w3c/sdw/issues/537
 - https://github.com/w3c/sdw/issues/538
 - https://github.com/w3c/sdw/issues/539
 - https://github.com/w3c/sdw/issues/540

Raise more if necessary

Kind regards,
Maxime