Fix MathJax centers equations

* Removes the MathJax heuristics that decides
  if equations are centered or left-aligned.
* Introduces the attribute display to specify
  if the math element is rendered in inline,
  display, or inline-displaystyle.
* add css rules for display / inline math images

Bug: 61051
Change-Id: Iba69903f781f0cb1606b8ddcffb90fb86c9b229b