Deduplicate Code

Problem:

The functions createViewCryptor2 and createFileCryptor2 essentially provide the same functionality: provide a read-only access to a document.

Consequences:

It is harder to understand and maintain what the two functions do.

Suggestions:

Merge the two functions and make them callable with and without a .

Drawbacks:

The of createViewCryptor2 is 16 bytes long, while the one of createFileCryptor2 has 24 bytes. Furthermore, createFileCryptor2 does not use the secondary signing key pair that is produced by createViewCryptor2.