Add a Memory Reader that owns the buffer via std::move

[Brett208]

Discussed in PR #373 as maybe useful.

Would be an alternative to the current MemoryReader that accesses a buffer owned by an external source.

Could provide additional guarantees of no changes to memory state when reading from a buffer that would be immediately disposed of after reading (I think a common use case).

Possibility of improved semantics in code from MemoryReader in some cases, but this idea hasn't been fully explored.