* Remove unnecessary self-dependency
* Regenerate core/default.nix and build -core via callCabal2nix
* grpc-haskell-core: -Wall -Werror and fix warnings
* grpc-haskell: -Wall -Werror and fix warnings
* Update documentation
* Remove LD_LIBRARY_PATH sets from usesGRPC
...as they no longer seem to be needed.
* Remove dead code
* Remove core/default.nix
...as suggested by @evanrelf.