Changes to the Show Answers page and the Essay Page

- The show answers page has been reformatted
- The problem grader and show answers page also now use mathjax to render equations
- The show answers page now allows wildcards 

Minor bugs : 
- mark correct didn't work on the problem grader and has been fixed
- achievements were a little wierdly formatted and this was tweaked
- fixed a bug where unformatted vectors were getting rendered as html in essay problems