Apply the Base Plugin when applying the HDVL Base Plugin

This gives us the standard lifecycle tasks that other plugins have.
Notably, this gives us the `clean` task, which deletes the entire build
directory, and a set of `clean<TaskName` tasks, which clean the outputs
of the respective tasks.

src/main/java/com/verificationgentleman/gradle/hdvl/HDVLBasePlugin.java

@@ -33,6 +33,8 @@ public class HDVLBasePlugin implements Plugin<Project> {
 
     @Override
     public void apply(Project project) {
+        project.getPluginManager().apply("base");
+
         final DefaultHDVLPluginExtension extension = new DefaultHDVLPluginExtension(project);
         project.getExtensions().add("hdvl", extension);
         project.getExtensions().add("sourceSets", extension.getSourceSets());