Initial implementation of JSON Writes[T] generator
Add id field to PlotObject
Rename Colors -> Color (object) to match its trait
JSON writers for enumerations
Add JSON writer for DenseVector
Make Marker a trait and inherit markers directly from BaseGlyph
Add JSON writer for sealed classes/traits
Rename PlotRange -> Range and make DataRange a trait
DataSource and Tool are now sealed
Initial version of JSON writers that compiles
Temporarily comment out location field
Anscombe example extends App