Major Description
The Blob.sha256() method can be really expensive as the MicroKernel doesn't keep track of that information and thus the method may result in a full scan of potentially gigabytes of data. Furthermore the method is only used for internal purposes.
Thus I suggest that we remove the method from the public Blob interface and keep the functionality only as an implementation detail for now. We can always bring back the method or something similar when there is real need for it.