Remove the blob.SHA{1,224}From{Bytes,String} constructors too. No
longer used. This adds blob.RefFromBytes which was missing. We had
blob.RefFromString. Now everything uses blob.RefFrom* instead of
specifying a hash function.
Some tests set a flag to force use of SHA-1 because there was too much
golden data to update. We can remove those one-by-one over time as we
fix up tests.
Updates #537
Change-Id: Ibe6428089a6221594c2b751f53f98b03b5a28dc2
Brad Fitzpatrick