Make only 2 generic logos for LTR and RTL

[mdebbar]

We have a lot of logo images in the web interfaces, and that's because we include some localized text inside the image. Let's try to remove that localized text from the image and add it in the HTML. This will reduce the number of images to only 2: one for LTR and one for RTL. The text could be positioned so that it appears inside the image.