Add Gradle

Right now, the project is very unstructured, if I may say so. When this pull request is accepted, the project will become more structured and manageable.

It lists instructions on how to build the project in README.md.

Changes:

* Added .gitignore
* Added Gradle
* Dependencies are now in the `build.gradle`.
* Moved source to `src/main/java`
* Moved files such as .properties to `src/dist/resources`. These are the files that should be placed in the main directory. Files ending in .sh and .bat are being parsed so they can include variables, which is in the lower section of `build.gradle`. This is to facilitate the changing of the file name of the `all` file.
* Added `sources` JAR, includes sources
* Added `javadoc` JAR, includes Javadoc
* Added manifest for JAR
* Added an `all` JAR, which includes all dependencies and the normal JAR.
* Added an `dist` ZIP, which is the distributable file for server owners.

When you need more information, please ask :)

I hope this pull request will be accepted even though this GitHub page hasn't been announced yet.