Refactored Blob slicing.
Refactored Blob slicing.

- Made 'raw_slice' and 'make_slice'. The latter is heavier, constructing a full
  Blob object, while the latter just returns a pointer to the slice.
- Also added new constructor to wrap a raw pointer in a Blob.

bkdoormaus/Glurg,bkdoormaus/Glurg,bkdoormaus/Glurg