Add encryption-at-rest to libraries

[hackerceo]

I would recommend the addition of using some block cypher encryption to the library so providing a filename and key (and probably IV aka Initialization Vector) an HDT is created or opened which has been encrypted.

The lack of this functionality is preventing HDT from being used in bioinformatics systems which contain sensitive medical information.

[D063520]

This remembers me to this:

https://www.semantic-web-journal.net/content/hdt-crypt-compression-and-encryption-rdf-datasets

not sure if it fully fits though