[cli] pulsar-client-tools supports end-to-end encryption

[massakam]

I enabled the pulsar-client command to encrypt message payloads.

How to use:

$ ./bin/pulsar-client produce \
  -m my-msg \
  -n 10 \
  -ekn my-app-key \
  -ekv file:///path/to/public.key \
  persistent://public/default/test

$ ./bin/pulsar-client consume \
  -s my-sub \
  -n 10 \
  -ekv file:///path/to/private.key \
  persistent://public/default/test

[eolivelli]

great! very useful.
I left a little comment about tests

[massakam]

Addressed the comments. PTAL