Add missing MathJax files

some files required for Mathoid were missing in the
modules/MahtJax folder

For example I15cb2d1cb0533a2fa0e21012198387501a3b42ea
requires AsciiMath and LaTeXML requires named entities

Change-Id: Ib7f2e4b8eb7250ea4fc24aac3cedf196211f38c2