Added and replaced image files

SDT/schema3.0/docs/images/Arg.png

SDT/schema3.0/docs/images/Array.png

SDT/schema3.0/docs/images/Constraint.png

SDT/schema3.0/docs/images/DataPoint.png

SDT/schema3.0/docs/images/DataType.png

SDT/schema3.0/docs/images/Device.png

SDT/schema3.0/docs/images/Doc.png

SDT/schema3.0/docs/images/Property.png

SDT/schema3.0/docs/images/RootDevice.png

SDT/schema3.0/docs/images/SimpleType.png

SDT/schema3.0/docs/images/Struct.png

SDT/schema3.0/docs/images/SubDevice.png

SDT/schema3.0/docs/images/TypeChoice.png