Improvements to MathJax-dev 

This is the work I've done to make the font generator configurable & automated and removes some files that are generated (thus should not be tracked). This also makes the packer path configurable, as requested by Dmitry (Debian).

Currently, this has been successfully used by the Dmitry and I to generate MathJax's fonts and data. Hopefully, this does not change how the generator behaves. It would be good if Davide could run it with his configuration to confirm that I haven't broken anything by doing this refactoring. The script developed for the new Open Type fonts are in a separate branch and is not ready yet.

The two last commits are not essential, they add an enumerateGlyphs script to enumerate the glyphs from a font (possibly Perl tables required by Davide's script). This is currently used by the open-type-fonts branch, but that might change in the future. I don't think it's a problem to include these commits anyway.