Include content from SotM-EU presentation

[pka]

I've added two parts of the presentation:

• Creating Shortbread Vector Tiles (more tools, tutorials, etc.)
• Customizing Shortbread (raw slides, full text missing)

For the second part I'm not sure in what depth this should be covered. IMO it is important to write about customizing, because this will be a common question when the osm.org tiles will be published. But maybe detailed tutorials should live in external blog posts or the OSM Wiki?

If there are no objections, I will add more text to the customization part.