domino-db: add a "read-All-items" method to the document class like document.readAllItems()

In some cases, it is hard to know what items are already in an existing document. In my use case, I want to display all items of a document in a list element in react. I also want to be able to do that with documents in apps where I do not know the schema of the document. Also, in a couple of applications, we have fields in documents that got created programmatically and these items are not reflected in forms or subforms and are only available in a subset of documents. To be able to read all items at once would save me expensive round trips to get to schema data instead I can interpret the canonical data format and act on the items accordingly.