added mathjax 2.3 to externals , and more logic for factorization

added mathjax 2.3 to externals , and more logic for factorization. Power
functions can be flattened to their smallest possible function.
 more logic for factorization

added mathjax 2.3 to externals , and more logic for factorization. Power
functions can be collapsed to their smallest representations. Created a
fluent intersection function for arrays.