new preferences API with configuration injection

src/main/java/org/aktin/Configurable.java

+package org.aktin;
+
+import java.lang.reflect.Method;
+import java.util.LinkedList;
+import java.util.List;
+
+/**
+ * Marker interface to allow automatic injection of configuration preferences
+ * 
+ * @author R.W.Majeed
+ *
+ */
+public interface Configurable {
+
+	public default List<String> getPreferences(){
+		List<String> prefs = new LinkedList<>();
+		Method[] methods = getClass().getDeclaredMethods();
+		for( int i=0; i<methods.length; i++ ){
+			Preference pref = methods[i].getAnnotation(Preference.class);
+			if( pref != null ){
+				prefs.add(pref.id());
+			}
+		}
+		return prefs;
+	}
+
+}

src/main/java/org/aktin/ConfigurationTest.java

+package org.aktin;
+
+public interface ConfigurationTest {
+
+}

src/main/java/org/aktin/Module.java

+package org.aktin;
+
+public abstract class Module implements Configurable{
+
+	public String getVersion(){
+		return getClass().getPackage().getImplementationVersion();
+	}
+	
+}

src/main/java/org/aktin/Preference.java

+package org.aktin;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * AKTIN preference. If the annotation is used, also implement the {@link Configurable} interface.
+ * 
+ * TODO add annotation processor to verify at compile time that each preference id is unique and method types are void(SingleArg)
+ *
+ * @author R.W.Majeed
+ *
+ */
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Preference {
+
+	String id();
+	String example() default "";
+	
+}

src/main/java/org/aktin/Preferences.java

+package org.aktin;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Preferences {
+
+	String group();
+	// TODO add Class<?> validator() to validate preferences
+}
\ No newline at end of file

src/main/java/org/aktin/prefs/Validator.java

+package org.aktin.prefs;
+
+/**
+ * Validates preference settings. 
+ * A validator may work for one or more preferences, 
+ * e.g for R executable (one preference) or email server settings (multiple)
+ * @author R.W.Majeed
+ *
+ */
+public interface Validator {
+
+}