Resolves issue #2 - Why static salt?

[jeff-winn]

I had to do a bit of restructuring on the code to support what needed to be done, so there will be quite a few new files added, and quite a bit of the logic that was within Main has been lifted out to other classes. Hopefully this will make the tool easier to maintain and make changes to in the future.

A couple things:

• I made sure tool still retains backwards compatibility for decrypt operations only, so it should be a minor upgrade rather than a major.
• The salt should be stored within secure environment variables along side the secret and passed into the tool. I've already made the necessary documentation changes to the README.md for this.
• I added FIPS compliance support if required people can use the new -fips option to enable this. This will cause it to use AES instead of Rijndael. Some companies may require using FIPS compliant algorithms.
• The key size and initialization vectors are currently quite small and their sizes should be increased. However, this will affect backwards compatibility so I opted to not touch this as it would indirectly affect your installation strategy on your servers.

If you have any questions, please feel free to ask!

[jeff-winn]

Going to close this and redo it, I was missing the console write for the generated salt.

[FeodorFitsner]

Sure. Fantastic work, thank you! Will look into your PR over the weekend.