Add alternate problem html template.

In regards to problem statement formatting, I think it is impossible to make a single option that will follow everyone's taste. I think it would be great to give plenty of template choices for HTML so that we could also inspire coders to make and share their own. Here is my alt1 problem statement template. The idea is that we can allow coders to say:

`shared.templateDef.problem-desc.templateFile = "builtin problem/alt1.desc.html.tmpl"`

Differences with default template:
* Dark gray background, light gray font low contrast.
* Images are not scaled down.
* ;html("grid") renderer option for parameter values, so that String[]s are rendered as grids if appropriate.
* Different output format. Mostly to allow the grid feature.