Add a Safe extension that allows you to restrict potentially dangerous features of MathJax when it is used in a shared environment (e.g., href to javascript, styles and classes, etc.)
Make MathML fontsize only be allowed if fontsize is 'all'
Use a service routine in MathML input to filter attributes (rather than override AddAttributes).  Also, make fontsize default allow all (authors can restrict if they want to).
Merge branch 'safe-mode' into develop

Conflicts:
	unpacked/extensions/TeX/bbox.js