SpatialGrid: Added getCellCount()
CallbackRepeater: Can now be paused and resumed
Bbox2, BezierCubic2: Added serialVersionUID
Mux/Demux: Fixed incorrect graphics generation
Main: Added onStartup() and onShutdown() placeholders
Added UserData placeholder class
EditorPanel: Now adds a bunch of gates of varying input counts
Merge branch 'SimulationDev'