Removed Setter

Since the setting cant be persisted to the config file it seemed
misleading to provide a setter.
Added GetSection support

Continuing to wrap ConfigurationManager functionality
Rearranging

Moving everything into the root of the project. Not enough tests at this
time to justify a bunch of folders.
Refactored AppSettingsReader

Changed the name of AppSettingsService to AppSettingsReader and added
some tests.
Updated Constructor

IAppSettingsService was changed to IAppSettingsReader