This inherits from the `Pref` system in `scala-utils`, extending it so
that preferences can be ScalaFX bound variables. This is the easiest way
to store things like the preferred window size and other per-user local
configuration.
This makes it really convenient to take a data structure like a
`ObservableBuffer`, which normally has special operations to watch for
different CRUD operations on its individual members, and treat the whole
thing as a solid value. This lets you turn it into an `ObservableValue`
where you get a notice of changes and then you can use the normal
operations like `map` and `flatMap` to react to changes.
Because this requires reprocessing the entirety of the contained values,
this may not perform as well as if you subscribe to more granular update
messages.
It is possible to round-trip these collections back to the ScalaFX
native collections using the other utilities available. This will be
required if you want to use the output to back something like a table.
