Merge: Expose LaTeXML Settings

Make LaTeXML setting configurable with the new global
variable $wgDefaultLaTeXMLSetting.

PS: This variable can be specified as an array or a
string. If specified as an array, the
 array('a'=>'b','c'=>array('d'=>'e','f'))
would be transformed to the equivalent setting
 a=b&c=e&c=f
,which is the input format for the LaTeXML daemon.

Conflicts:
	Math.php
	MathLaTeXML.php
	tests/MathLaTeXMLTest.php

Change-Id: I1fb2d1c4fc7e6d2b6f9cf31756b297b1a92809db