Fixed bug where an asset's name was not being returned.
Wrapped the YahooFinanceAPI class in an interface (StockDataPortal) to hide the implementation on where/how the data is retrieved from the MarketData class.
Created app.config file to specify application-specific settings. The list of available Stock data (Symbols.csv) is currently specified in there.

The Symbols.csv file has been placed into a data/ folder. The project has been set up to copy the data/ folder into the bin/ directory when debugging/running the application.