[predicates] keep making `yes` predicate importable from cubicweb (closes #2790319) The `yes` predicate was moved out in CubicWeb 3.15 but it should have remained importable from the cubicweb.predicates module, for bw compat reasons and also because logilab.common.registry is an implementation detail.

[views/tables|css] backout rev 895e34d9ae0d This changeset introduced a GUI behaviour change that has usability side-effects (eg. shows a non-undoable massive action as a first-class action). The idea is good, but it requires a better implementation; tabs are not the proper GUI solution to the original usability issue.

[webconfig] cleanly handles ``fckeditor_installed`` when no uiprops The previous version of the code relied on a default value with a dummy ``FCKEDITOR_PATH`` entry. The new code check if uiprops is initialized or not.

[webconfig] fallback to default configs if https ones are not defined When cubicweb serves a request with an https scheme, it tries to access ``https_uiprops`` and ``https_datadir_urls``. However if those are not defined we should fallback to unsecure url instead of crashing with a traceback. There are very valid usecases for undefined https url. For example if your ``base_url``, ``datadir_url`` and uiprops content are already https urls. Closes #2786643

[webconfig] explicit some webconfig attribute Explicit declaration of attribute are much clearer. Just do it.

merge 3.16.x fix in 3.17.x branch