Various fixes and performance improvements

[pupnewfster]

• Switched to gradle to allow people to easier fork, compile, and then make pull requests. This also makes changing dependency versions easier.
• Cleaned up many unneeded declarations and older coding styles (very slightly improving performance with having less calculations.
• Updated Java to Java 8, as Minecraft requires Java 8 (It may have already been compiling with Java 8 but was impossible to tell.
• Removed some unnecessary checks such as checking if a returned ItemStack is null. (As of Minecraft 1.11 ItemStacks cannot be nulll by definition)
• Better handles duplicate checks of same method improving performance.
• Fixed some spelling mistakes.
• Implemented a more advanced version of #24 removing warnings of lag spikes.
• Improved WPT_DO_DIFFUSION to not throw warnings of taking too long with default timeout warning.
• Fixed logic of diffusion. It used to load the same chunk multiple times (or at least did on my world) and then it would end up just having a net loss even if the chunks around it had a lot more pollution.

[kabachuha]

Thank you for this hard work. I've viewed your PR and I'm going to merge it soon, but I think that I should first improve the config versioning system to avoid possible conflicts with new PollutionSources.

[pupnewfster]

One way is you could package the latest version in the jar. And if a pollution source is missing it looks for what value it has in the packaged version.

[pupnewfster]

Do you have any idea when you will come up with a better config versioning system or should I revert the spelling corrections to the config so that this can be accepted?

[kabachuha]

I think I would implement forge-like JSON versionising system(file on the GitHub with a map like [supported versions]-[URL to config file]).