WSJ, Yahoo!Finance, and Bloomberg datasource added to RiskLib.NET with examples

I added 3 datasource to RiskLib.NET to demostrate how to implement two different interface: IDailyClosingSource, IHisotricalSource, and a special designed datasource: Bloomberg. I also added a example to retrieve data from these datasources.

Although there are still a lot should be modified, the example worked fine to retrieve data from these datasource.