WIP: [NX-529] Add OCompression impl to encrypt records

https://issues.sonatype.org/browse/NX-529

TBD: Have UserTokenStorage impl register an instance of this, plus test updates. Also need to specifically test whether export keeps the records in encrypted form somehow, or decrypts them.
+1 for changing the name to EncryptedCompression (or PbeAesCompression if you want to be more specific)