Replace Ant with Gradle and fix Unit Tests

Gradle gives Maven/Ivy abilities, and (in theory) the ability to provide compatibility with IntelliJ while reduceing the amount of code.

Gradle Wrapper is included for easy installation. I plan to write some detailed instructions later.

There are unit test errors that are from RequirementManager that cause 'gradle build' to fail, which I plan to look over and hopefully fix when I get some more free time later.

This will likely cause issues with the other pull requests, which I am more than happy to help fix, as they still use Ant, but consider this a functional proof of concept. :)