[cwconfig] Add optional configuration param to load a UI cube before other cubes Needed later on to load UI cubes such as legacyui, and one day squareui.

[web/views] Move massmailing to its own cube (closes #2788086)

merge with stable fix

[req] explicit `user` attribute The `RequestSessionBase` object needs a `user` attribute. It is initialized by sub class, but having it explicitly declared is much cleaner.