Add Java example

[paulhowardarm]

Summary

Add a Java client example to the demo, structured along the same lines as the Rust and Go demos.

Details

The Java program can use the low-level Java client library as opposed to the JCA stack, which would make it smaller and simpler. To behave like the existing programs, it should be a single, self-contained console executable that reads a line of text from standard input, base64-decodes it, and decrypts it using the PsaAsymmetricDecrypt operation using the key HelloParsecDemoKey (which will have been provisioned by the demo script, so the program does not need to create it). The decrypted plaintext should be converted to a string and written to the console standard output.

Once this program has been added, the demo script will also need to be updated to invoke it. It should be self-evident how to do this from the existing contents of the script. The plaintext string should be "Hello Parsec from Java!" to match the existing strings.

Dependencies

This can't be done until the JAR for the Java client library is published to a well-known location (such as Maven central or some other canonical repository). This requirement is being tracked here: parallaxsecond/parsec-client-java#17