Kara Swisher does a great job of covering all the changes. After being spotted in Yahoo’s cafeteria getting her own lunch, Mayer added a weekly all-hands Friday afternoon meeting to the schedule. At the first of these meetings, she announced that the food at Yahoo’s URLs Cafe in Silicon Valley would be free from now on. For those who don’t know, Friday afternoon all-hands meetings and free food in the cafeteria are classic Google staples. And more seem to be coming. Mayer seems to be planning big changes to the layout of Yahoo’s work areas and buildings. The idea would be to foster a more col…