Cleaned up and exchanged Ant for Gradle

* removed built files like `*.class` and `*.jar` that can be recreated by running Gradle
* removed the files created by NetBeans
* removed configuration-files for Ant
* moved source files to `src/main/java` and `src/test/java`
* excluded the examples from the build
* updated README
* added LICENSE (as the blogpost doesn't mention a license, I took the one from SwingLabs, as MultiSplit is part of SwingLabs)

Author: floscher

.gitignore

@@ -1 +1,11 @@
 /build
+# Gradle
+/.gradle
+# Eclipse
+/.classpath
+/.project
+/.settings
+# IntelliJ IDEA
+*.iml
+*.ipr
+*.iws

LICENSE

@@ -0,0 +1,29 @@
+## MultiSplit
+
+This is a copy of MultiSplitPane and MultiSplitLayout as found [in a Java.net blog post by Hans Muller](https://today.java.net/pub/a/today/2006/03/23/multi-split-pane.html) (you can also download the original source code [from there](https://today.java.net/pub/a/today/2006/03/23/multi-split-pane.html#resources)).
+You'll also find MultiSplitPane, MultiSplitLayout in the SwingLabs project, see https://java.net/projects/swingx.
+
+## Gradle build
+The build system of the master branch has been switched over from Ant to [Gradle](https://gradle.org), so you need Gradle installed (tested with Gradle 2.2.1, but should also work with much lower versions).
+
+As this is a Java project, you of course also need to have the Java Development Kit (JDK) installed. By default this project builds for Java 1.7, but if you want you can change that in `build.gradle`.
+
+### Command line
+In the command line you can simply use the following to build into the `build/` folder (`build/lib`):
+```shell
+gradle build
+```
+
+### Eclipse
+If you want to open the project in Eclipse, just type the following in the command line, which generates some Eclipse project files:
+```shell
+gradle eclipse
+```
+Now you can open the project as an Eclipse project.
+
+### IntelliJ IDEA
+For opening the project in IntelliJ IDEA, you can use the following command from the command line:
+```shell
+gradle idea
+```
+Now you can open the project as an IDEA project.

README.md

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+apply plugin: 'java'
+apply plugin: 'eclipse'
+apply plugin: 'idea'
+
+repositories {
+  mavenCentral()
+}
+dependencies {
+  compile 'junit:junit:4.11'
+}
+sourceCompatibility= '1.7'
+targetCompatibility= '1.7'
+sourceSets {
+  main {
+    java {
+      exclude 'examples/*.java'
+    }
+  }
+}