support calling `Grapher.redraw` multiple times
support calling `Grapher.redraw` multiple times

`Grapher.redraw` optionally accepts new options, and redraws according
to those options.

It's a little heavy handed, but allows redrawing without re-computing
track or profile slices.

refs Programming:#864 (.25)

NProfileAnalysisComputationalTool/npact,victor-lin/npact,NProfileAnalysisComputationalTool/npact,victor-lin/npact,NProfileAnalysisComputationalTool/npact,NProfileAnalysisComputationalTool/npact,NProfileAnalysisComputationalTool/npact,victor-lin/npact,victor-lin/npact,victor-lin/npact