Added A2CS Data Model

[ts-exsensio]

No description provided.

[albertoabellagarcia]

• DIH2/A2CS/OEEMetric/doc/spec.md is not necessary, however, its contents have to be located into the schema.json according to the manual contribution_manual
• DIH2/A2CS/OEEMetric/schema.json have many required properties, it should be considered to reduce this amount
• DIH2/A2CS/Product/doc/spec.md (same as previous spec)
• DIH2/A2CS/Product/schema.json EntityIdentifierType is a relationship, see contribution_manual , https://github.com/ts-exsensio/DataModel/common-schema.json#/definitions/TimeSpan is a 404. some doubts if product has to be an Entity.
• DIH2/A2CS/Station/doc/spec.md (see other spec)
• Station is a very generic name. I guess it could be more specific.
• DIH2/A2CS/Station/schema.json see same comments as the previous schema
• DIH2/A2CS/common-schema.json further info why it should be necessary to include the patterns