More support for ISO 8601 WeekYear and WeekOfWeekYear

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At a minimum we should be able to construct a LocalDate from the WeekYear and 
WeekOfWeekYear.  Something as simple as:

new LocalDate(2012, 1, IsoDayOfWeek.Tuesday); // WeekYear 2012 Week 1

As evidenced by 
http://stackoverflow.com/questions/11342856/localdate-from-week-and-weekyear I 
am not the only user that has needed this.

More advanced support, the need for which is hinted at in a comment on the 
stackoverflow answer, would be to have a type to represent a week.  I would 
also find this helpful and would it fit better with the Noda time approach.  
Something like:

var week = new LocalWeek(2012, 1);
var date = week.On(IsoDayOfWeek.Tuesday); // create a LocalDate
date.Week // Get the LocalWeek for a date

The LocalWeek would be a year and week only.

Original issue reported on code.google.com by WalkerCo...@gmail.com on 11 Oct 2012 at 8:58