For next release:
+ Move all of the legacy-adapter stuff to a new LegacyAdapter directory.
Use David's boingeeFieldTrip adapter as a basis. Separate out all of
the GLUT stuff.
+ Much-simplified interfaces. FRP.Reactive has just behaviors and events.
FRP.Reactive.LegacyAdapter for building legacy adapters.
+ Something for accessing representations but not exposed in FRP.Reactive.
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Beyond:
+ Revisit choice of time as double. Consider nanoseconds or microseconds
instead, for regularity of time-stepping.
+ Semantics-based fusion rules. Inquire about fusion vs sharing.