Rename the Timelapse panel to the Recordings panel, since it shows
recordings and their details. Closes #118.
Rename TimelapseGrid to RecordingInputsGrid.
Add missing license blocks for RecordingsPanel files.
Implement ReplayTask and ReplayTaskScheduler, a simple interface for
running queued asynchronous tasks.

These will be used to manage workflows currently achieved with lots of
scattered checks, such as breakpoint scanning and Recording management
during capture.
Implement Automemoized specialization for SerializedScriptValue. History.state is now memoized. Closes #152.
Frontend: convert to putting __proto__ inside the prototype object literal, rather than assigning it later.
Add Object.prototype.onceEventListener(), which wraps listeners that should detach after firing once.
Add cancellation to ReplayTask, ReplayTaskScheduler.
Make ReplayTask and ReplayTaskScheduler methods chainable.