[dataimport] Uniformize the API across the different stores.
This is achieved by modifying the ``relate`` method
so that it takes an extra ``**kwargs``.
More specifically, ``SQLGenObjectStore``'s ``relate`` method
needs the the type of the subject entity which is passed through
``**kwargs`` as the ``subjtype`` keyword argument.
Actually, it is the ``add_relation`` method of the
``SQLGenObjectStore`` who needs this argument. However, as
this method is not called directly (but via the ``relate``
method), the ``subjtype`` argument is passed to
``add_relation`` via ``relate``.
The other stores' ``relate`` methods do not need this
extra argument, hence for the other stores ``**kwargs``
is empty.
In this manner, the API is unified across the different stores.
What's new in CubicWeb 3.17?
============================
New functionalities
--------------------
* add a command to compare db schema and file system schema
(see `#464991 <http://www.cubicweb.org/464991>`_)
* Add CubicWebRequestBase.content with the content of the HTTP request (see #2742453)
(see `#2742453 <http://www.cubicweb.org/2742453>`_)
API changes
-----------
* The SIOC views and adapters have been removed from CubicWeb and moved to the
`sioc` cube.
* The web page embedding views and adapters have been removed from CubicWeb and
moved to the `embed` cube.
* drop typed_eid() in favour of int() (see `#2742462 <http://www.cubicweb.org/2742462>`_)
Deprecated Code Drops
----------------------
* The progress views and adapters have been removed from CubicWeb. These
classes were deprecated since 3.14.0. They are still available in the
`iprogress` cube.
* API deprecated since 3.7 have been dropped.