Port to 7.x-2.x: Use CSS for the loader

This is a port of issue #1040460: Use CSS for the loader to the 7.x-2.x branch.

It would be better to provide a loader with CSS instead of hard coding the image asset into the javascript file.

Original report:
It would be good if the loader image used css rather than a hard coded img tag. That way a themer could use CSS to override the look of the loader quickly without having to hack into the module or override the theme function. You could use the standard views loader by default by giving it a class of views-throbbing.

I haven't got CVS sorted yet so can't make a patch but replacing line 32 in views_infinite_scroll.js with:

var img = '

';

worked fine for me