Add hash property to schema

[jvdsn]

Many algorithms rely on hash functions. This commit adds an enum property and a list of commonly used hash or extendable output functions.

fixes #896

[stevespringett]

FYI, CycloneDX has a hash property with most of these enums. It's located in the common schema.

specification/schema/2.0/model/cyclonedx-common-2.0.schema.json

Line 47 in 0f8a254

"hash": {

As written, this PR mostly duplicates the common structure used throughout the specification. An argument can be made that the hash structure should be moved to the cryptography schema, though.

[jvdsn]

@stevespringett it seems like that property is intended to be used as the hash of the object (the value), whereas the property I propose here is the hash used by the object (i.e. the cryptographic algorithm by itself). I do see the point about there being potential confusion, so maybe what I'm proposing should be renamed.

[stevespringett]

And we'll need to centralize the algorithms so they can reused across all the use cases.

[jvdsn]

@stevespringett I'll try to clarify on the call what the purpose of this property is. I think it's easier to explain in words than through text.