Move to a single solution file containing all of the C# projects, but no other solution folders - it's easier to edit those files outside VS than keep adding and removing them from the project.
The AddressBook protos have been regenerated (with a change to the example proto which I haven't included in this change - I'll wait for us to decide exactly what we're doing with namespaces before changing protos outside the csharp directory.

Note that now we've got Addressbook.cs which contains AddressBook and Addressbook classes. It's bad enough that we've got a class called AddressBook within a namespace of AddressBook (hard to get away from) but having things vary just by case is nasty.
This is more evidence that an option for renaming the file and descriptor class would be welcome. (A single option can probably handle both.)