Gradle: Always apply JavaBasePlugin, otherwise startup may fail with …

…new plugin DSL, as initialization order is undefined. This closes #144

src/main/resources/de/thetaphi/forbiddenapis/gradle/plugin-init.groovy

@@ -18,11 +18,8 @@
 
 import java.lang.reflect.Modifier;
 import org.gradle.api.plugins.JavaBasePlugin;
-import org.gradle.api.plugins.PluginInstantiationException;
 
-if (project.plugins.withType(JavaBasePlugin.class).isEmpty()) {
-  throw new PluginInstantiationException('Forbidden-apis only works in projects using the java plugin.');
-}
+project.plugins.apply(JavaBasePlugin.class);
 
 // check if running in Gradle Daemon?
 // see: http://stackoverflow.com/questions/23265217/how-to-know-whether-you-are-running-inside-a-gradle-daemon