Change the AutoValue pom.xml so that it uses the Maven shade plugin to i...

Change the AutoValue pom.xml so that it uses the Maven shade plugin to include all dependencies in the generated jar, and to rename most of them. This is intended to address https://github.com/google/auto/issues/156.
Actually, this fact makes using velocity in multiple processors dangerous, in case of version skew. :/  Since I don't think processors get their own class loader, they may collide.