Add an “Area” data-type into CAMARA_common.yaml

[tlohmar]

Problem description
Commonalities started the discussion of adding an Area Data-Type into CAMARA_common.yaml, in Issue #242.
A couple of potential modifications and extensions are identified. Please provide your views on the issue.

Expected action
Please provide your views on the issue.

[rartych]

Please review the PR for this issue camaraproject/Commonalities#315 .