Switch AES-128 to AES-256

[yonas]

Is there any reason to be using 128 instead of 256?

[thequailman]

For most folks, AES-128 is a better choice than AES-256--it's faster, and in some situations more secure than AES-256 with regards to related key attacks. AES-256 could be added as an option, but ChaCha20 would still be the best symmetric encryption for most folks from a performance/security perspective.

Definitely not opposed to seeing it in here--if someone wants to add AES-256 support, please PR it.

[thequailman]

AES-256 is now available as an algorithm choice.