The metadata paths are sometimes represented with a slash as a separator, sometimes with a dot. We should make that more coherent:

• Model metadata paths should be represented with a slash, i.e. "title", "composite/repeater/meta" and "content/content2/title". In some cases, relative paths can be handled like "../../meta".
• Stored metadata paths should be represented with a slash, and with indices for repeater entries, i.e. "title", "composite/repeater[3]/meta" and "content/content2/title"
• The APIs accepting those paths should be clarified and centralized
• Unit tests should be added