The backup module has been renamed so that it isn't confused with a
controller. The "backup controller" has never managed any state or
extended the controller base class. It is a module for backing up data,
but it's not a controller.
The backup controller's current inclusion in the `store` and `memstore`
`ComposableObservableStore`s was getting in the way of some other
enhancements to that class (which will come in a later PR).
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