EditorWorld: getWorldExtent() now handles the world being empty
SpatialGrid: Made serialisable
VecPath: Changed to wrap rather than extend due to API design flaw
preventing serialisation
EditorPanel: Moved debug/demo stuff into its own function
GUI: invoke addDebugAndDemoStuff()
CommonActions: Added actions to deal with undo/redo GUI logic
Editor menu/toolbar controllers: Added undo/redo handling
HistoryManager: Added change listener mechanism
Tool: Added markHistoryChange()
HistoryManager: Fixed bug in state indexing causing desync
EditorWorld: Added toString()
EditorPanel: Debug stuff now has a few undo/redo steps to show