[test] update sobjects/test/unittest_cwxmlparser to cw 3.19 api

[repo] make it clear in internal_cnx that security is disabled as explained in its docstring. It was previously relying on internal connection's fake user (InternalManager) for read security and on disabling security hooks for write security. Using the security_enabled context manager is more readable and more reliable: while the older implementation works thanks to the InternalManager associated to the session, custom hooks should rely on session.[read|write]_security being correctly set. This change also allows selecting Password attributes in internal connections without explicitly disabling read security.

[datafeed] update datafeed internals to use connection instead of session

[test] update sobjects/test/unittest_notification to cw 3.19 api

[test] simplify setup of sobjects/test/unittest_supervising.py

[test] update sobjects/test/unittest_supervising to cw 3.19 api

[test] update sobjects/test/unittest_email to cw 3.19 api

[wsgi] the spec says wsgi.url_scheme *must* be provided No need to be defensive, anything else is a bug in the gateway.

[shell] provide autocompletion for rql queries in cubicweb-ctl shell (closes #3560541) Use the ``rql.suggestions`` component to complete user's input - readline calls the ``complete`` method with user's input, - the ``complete`` method asks for each known completers if it can suggest completions for user's input.

[book] avoid '~' in all-in-one.conf, it is not expanded Closes #3753213