Package to support SVG graphics and file graphics in WWPlot system (WeBWorK2 Portion)

Dear Mike,

I think the package of modules and related files to support SVG graphics as well as file graphics in the WWPlot system is ready for other to try out.

This is the pull request to pull the modules and related files from the develop branch of my copy of webwork2 into the develop branch of openwebwork/webwork2.

Sincerely,

Bill