Add Cipher CLI example for CBC/CTR API

[skmcgrail]

$ cargo run --example cipher -- --mode ctr encrypt "Hello World"
key: b331133eb742497c67ced9520c9a7de3
iv: 4e967c7b799e0670431888e2e959e154
ciphertext: 88bcbd8d1656d60de739c5

$ cargo run --example cipher -- --mode ctr --key b331133eb742497c67ced9520c9a7de3 decrypt --iv 4e967c7b799e0670431888e2e959e154 88bcbd8d1656d60de739c5
Hello World

$ cargo run --example cipher -- --mode cbc encrypt "Hello World"
key: 6489d8ce0c4facf18b872705a05d5ee4
iv: 5cd56fb752830ec2459889226c5431bd
ciphertext: 6311c14e8104730be124ce1e57e51fe3

$ cargo run --example cipher -- --mode cbc --key 6489d8ce0c4facf18b872705a05d5ee4 decrypt --iv 5cd56fb752830ec2459889226c5431bd 6311c14e8104730be124ce1e57e51fe3
Hello World

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