Support PDF output via LaTeX

Hi,

I apply changes the new code base. Diffs now seem easier to read.

I copy comments from the last pull request:

Adding LatexFormatting to CodeFormat and Markdown project is relatively easy since I can follow the structure of HtmlFormatting. However, `Literate.fsx` is quite messy since it assumes HTML as the only output format. Maybe it needs to be cleaned up a bit.

Status:

- F# source codes are rendered correctly. I create two template `template-color.tex` with colorized source code and `template-math.tex` with a few tokens being converted to math symbols.

- Markdown rendering is tested with a few big files from `testfiles`.