Save a figure file with `GraphOptimizationApplication.draw`

[t-imamichi]

What is the expected enhancement?

It would be useful if GraphOptimizationApplication.draw can not only draw a figure on a jupyter notebook, but also save a figure file (png, pdf, jpeg).

[a-matsuo]

Currently, matplotlib is used with networkx to draw a graph. However, we might change the library for visualization. @mtreinish is working on, so please leave this issue for now.