Originally, most of the sources used constructor parameters to set the
various options of the source. Although convenient, it was difficult to
keep track of what each parameter meant. To make the code more clear,
source parameters are now set with accessor functions (e.g.
`SetPointDimensions`). Although this makes code more verbose, it helps
prevent mistakes and makes the changes more resilient to future changes.
This matches the output field name in VTK and ParaView for the
equivalent source. This change allows this source to be used as a drop-
in replacement for the VTK source (which could be very useful).