[datafeed] Allow to override use_cwuri_as_url in configuration of a datafeed source This is necessary because in some case one will want to write parser which create entities not one-to-one related to entities from the distant source (for instance see the `vcrs` cube which create entities holding statistics for code review, while not importing review entities themselves). Ideally we should provide a way to the parser to indicate the source that cwuri should not be used, but that's a start... Closes #3670210

Schema of the data
------------------

First take a look at the data schema_ then try to remember that you are browsing
through a heap of data by applying stylesheets to the results of queries. This
site is not a content management system with items placed in folders. It is an
interface to a database which applies a view to retreived data.

.. _schema: schema