Part of fixing https://github.com/grpc/grpc/issues/2192

- Remove the launch screen.
- Add a label explaining where to look for the code and results.
- Delete unnecessary boilerplate code.

The tests are going to use it too

That file is already deleted on master

Generated by running protoc --objc_out=. --objcrpc_out=. *.proto in this directory.
Generates separate files until GeneratorContext::OpenForInsert/Append works.
A temporary podspec for the proto3 runtime is being used, pending the official.

Still missing: retrieving prefix from file option.

When Podfile.lock is present, the prepare_command of the gRPC pod isn’t
executed on “pod install”, even if the Xcode workspace and the Pods/
directory are absent.