Remove Twisted web server Twisted web server is not used anymore and has been superseded by pyramid many years ago. Furthermore, our usage is not compatible with Python 3. So we drop the "etwist" sub-package. As a consequence, "all-in-one" configuration type gets dropped as it was Twisted-specific. We resurrect it in cubicweb/pyramid/config.py by only keeping options used by the "pyramid". Similarly, we introduce a AllInOneCreateHandler in cubicweb/pyramid/pyramidctl.py that is basically the one that lived in cubicweb/etwist/twctl.py and is used to create the "all-in-one" instance. Added a TODO here about "pyramid.ini" that could be generated at the end of bootstrap() method. In cubicweb/devtools/httptest.py, CubicWebServerTC is now equivalent to CubicWebWsgiTC and the latter is dropped.

Templates
---------

*Templates* are specific views that do not depend on a result set. The basic
class `Template` (`cubicweb.common.view`) is derived from the class `View`.

To build a HTML page, a *main template* is used. In general, the template of
identifier `main` is the one to use (it is not used in case an error is raised or for
the login form for example). This template uses other templates in addition
to the views which depends on the content to generate the HTML page to return.

A *template* is responsible for:

1. executing RQL query of data to render if necessary
2. identifying the view to use to render data if it is not specified
3. composing the HTML page to return

You will find out more about templates in :ref:`templates`.