A little preliminary work on primitives
ScalarContainer
MapContainer implemented
SliceContainer
Add Traverse function
Initial work on docstate and primitives
SetPrimitive.Apply
Fully implemented primitives
Move SetPrimitive into its own file
Move DeletePrimitive into its own file
Simplify Container interface
No docstate history for now
DocumentState.Reset
Remove old state code from logic package
Add State field to Document
logic.Event.getPrimitives() implemented for SET