Implement OpenSslEngine.getSupportedCipherSuites() and get/setEnabledCipherSuites()

Motivation:

To make OpenSslEngine a full drop-in replacement, we need to implement
getSupportedCipherSuites() and get/setEnabledCipherSuites().

Modifications:

- Retrieve the list of the available cipher suites when initializing
  OpenSsl.
- Improve CipherSuiteConverter to understand SRP
- Add more test data to CipherSuiteConverterTest
- Add bulk-conversion method to CipherSuiteConverter

Result:

OpenSslEngine should now be a drop-in replacement for JDK SSLEngineImpl
for most cases.