Allow Mathjax(Latex) in Student responses

Currently, Latex rendering is only supported for question prompts in ORA2. This
commit introduces Latex rendering in ORA2 peer assessment
view, self assessment view, grade view, and staff-info view. The reason that
this Latex rendering code is inserted directly into ORA2 is that edx-platform,
does not know when to start Latex rendering for ORA2 views that come in via
AJAX. This is a much needed feature for many classes. 
Let me check if I'm understanding it right: 
1) Add "latex_response" class to appropriate tags(probably div) for each view. 
2) in oa_server.js render() check "allow_latex" in the settings, and if true Call MathJax for the given element. Add MathJax code snippet in the .done() callback block, after resolveWith()