Cleanup itex extension

Most of the DOM manipulations can be done
before doing the AJAX call. This leaves
just the insertion of the MathML nodes in the
mrow for the AJAX callback function.

Also, make the stroke-width for the connector tool 
default to 2.

public/svg-edit/editor/extensions/ext-connector.js

@@ -305,7 +305,7 @@ $(function() {
 								"id": getNextId(),
 								"points": (x+','+y+' '+x+','+y+' '+start_x+','+start_y),
 								"stroke": '#000',
-								"stroke-width": 3,
+								"stroke-width": 2,
 								"fill": "none",
 								"opacity": .5,
 								"style": "pointer-events:none"