The key storage module didn't comply with Android coding standards
and had room for improvemnet in a few other ways, so have cleaned up.
Change-Id: I260ccff316423169cf887e538113b5ea400892f2
Instead of writing raw keys, encrypt the keys with keymaster. This
paves the way to protecting them with auth tokens and passwords later.
In addition, fold in the hash of a 16k file into their encryption, to
ensure secure deletion works properly.
Now even C++ier!
Bug: 22502684
Bug: 22950892
Change-Id: If70f139e342373533c42d5a298444b8438428322