AisMessage::getEncoded is largely untested

[Zoybean]

The test suite does not cover the getEncoded method of most messages, and the tests which call that method are heavily obfuscated, making it unclear what messages are being tested without debugging the tests as they run.
During debugging, aisDecodeEncode only tested getEncoded in messages 1, 3, 4, 5, and 24 (assuming the changes in #37), and the rest of EncodeTest only covered getEncoded in the above messages and message 12. Overall, only messages 1, 3, 4, 5, 6, 8, 12, 18, and 24 had their getEncoded methods called in any test methods.

[tbsalling]

Hi @Zoybean - thanks; your contribution is welcomed.

It would be a great help if you could send me a pull request with the changes you propose.

Thanks,
/Thomas.

[Zoybean]

I would attempt to write a test covering this class, however as I mentioned the existing tests are heavily obfuscated and hardly documented, and as such I am unsure of how to make a test string to test a specific message. See decode_encode_messages.txt for an example of the test strings I would need to add to.