[server/utils] add_looping_task can be used any time (closes #2408814)

[formrenderers] if a tag object gets there, it blows (closes #2410462) - cwtags monkeypatches cubicweb's UStringIO's .write and .getvalue methods - but it cannot monkeypatch list.append ...

[login] redirect to real instance root if no postlogin_path is provided When not postlogin_path is provided, the login form issue a redirect to "/". The instance root may not be at "/" on the server. Then issuing a redirect to "/" send the user to the wrong location. We now redirect to "." which works fine because the "login" controller a direct children of instance root (http://babar.com/instance/login). All other redirection of the login controller use relative path too and then rely on this relative path from the login controleur to the instance root. This mechanism may be considered fragile and may deserve a proper fix. but this is to be discussed and implemented in another changeset.

[web/application] declare default 'content' value sooner (closes #2406560) It may be used while processing AuthenticationError. Such error may be raised before the former declaration.

[views/tabs] fix rql/eid param conflict when either one is already in the request form (closes #2405249)

Added tag cubicweb-debian-version-3.15.1-1 for changeset fe5e60862b64

Added tag cubicweb-version-3.15.1 for changeset 783a5df54dc7

[debian] prepare 3.15.1-1

[server/tests] fix tests

[registry|ajaxcontroller] the @ajaxcontroller decorator ought to return a compatible object (closes #2385155)