Xubuntu slideshow does not support RTL

Please grant a freeze exception for the following as this allows the Xubuntu slideshow to support RTL languages. The upload also updates translations from Launchpad, prunes unused translations (freeing up a small amount of space), and uses a higher resolution image of the personalize icon (the previous one was slightly pixelized).

Original report follows:

The Xubuntu slideshow does not support RTL. The script adds the rtl class to the correct element, but there is no CSS to handle it.

Unfortunately, the problem isn't dead simple to fix: bullet points are illogically aligned to the left of list items via the li:before selector, and there is also an li.nobullet class.

Thankfully, I just learned something! It _is_ possible to set list-style for individual LI elements; it isn't a global property for the entire list at all. Shouldn't be hard to remove the use of :before and maintain the same functionality, which will also magically support RTL. The rest should be pretty easy.