Standardise artifacts and Version in Gradle

To explain my changes:
- `archivesBaseName` is actually used as the project name when deploying to maven. It would be better to keep the project name constant on maven so I put the mcversion into the version string instead.
- A jar with the classifier "sources" is automatically loaded by most IDEs when artifacts are resolved by maven. Because of this I added a sources artifact.
- I replaced the devJar with the deobfJar because this name more accurately describes the contents, and I make this a standard on my jenkins.
- I also replaced the version string building with string interpolation because it's cleaner.
- I added some gradle gitignores[.](https://github.com/github/gitignore/pull/1071)