Remove all `background="image.jpg"` references in favor of inline css

[Ted Goas]

Did some light Litmus testing and it seems <td style="background-image:url(image.jpg);"> is well supported on its own with a color fallback. I haven't found an instance where adding <td background="image.jpg"> has improved rendering.

Rémi Parmentier [2 days ago]
I'm number 2 since support was added in Outlook.com last november. Not sure there's any benefit to add the HTML background attribute unless you want Lotus Notes < 7 support.

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Worth noting: