Add a CMake Register Worker function that can be installed.

This is going to be packaged with Remus, so that users of remus can
easily generate .rw files for workers they write.
Update all examples to use the new RegisterWorker call.
Cleanup the testing mesh worker code.

No need to have RemusWorker*rw*in files.
Merge pull request #121 from robertmaynard/install_register_worker_cmake_files

Install register worker cmake files