This refactors and removes most of the internal loader/hash/hash.hpp, keeping only the very Geode-specific sha256Text method that ignores \n and \r characters.

Instead, there are now public SHA256 utils in the Geode/utils/hash.hpp header: both a stateful Sha256Hasher for incremental hashing and one-shot sha256 functions. As well as a shared Hash class, allowing users to choose whether they want a binary digest or a hex form.