@DataContructor annotation

Inspired by the discussion at https://groups.google.com/forum/?fromgroups=#!topic/xtend-lang/nOm63mi2Zfw I've written this little active annotation.

As you host a collection of other useful annotation I thought I'd contribute.

Usage:

	class Person {
		@DataConstructor
		new(String name, int age) {
			println("Person created");
		}
	}
	
The above is equivalent to:

	class Person {
		public final String name;
		public final int age;
	
		new(String name, int age) {
			this.name = name
			this.age = age
			println("Person created");
		}
	}

PS. I've also set java source & target to 1.6 in main pom .