Add javascript or xpath libraries

[AndreG-P]

I was wondering if we should add libraries that can be used independently of Java and Maven. The idea came up since we are facing same or similar issues with MML in VMEXT (see gipplab/vmext#28).

I'm not sure if it is worth to provide a whole javascript based API of our MathMLTools project (maybe in distant future). But I think a good idea would be a library of useful XPath commands. Perhaps a YAML file accessible from one of our servers.

What do you think @physikerwelt @vstange?

[physikerwelt]

Yes. Can you make a proposal what the core functionality of the libraries should be. It would be nice to use the same API in all languages.