ContentBlock refactoring

The business logic inside the ContentBlockController was moved to the ContentBlockModel.

The Ninject library was added to the project.

The ContentBlockController now resolves its ContentBlockModel trough the new ControllerModelFactory inside the feather project by passing a dictionary of constructor parameters, both the ContentBlockController assembly  and its inheritor assembly if applicable. The ContentBlockController assembly contains a NinjectModule inheritor named "InterfaceMappings" which describes the bindings which Ninject will use to resolve instances of specific class.

The feather-widgets project now comes with a specific feather dll instead of getting it form NuGet. This way we can get the latest feather without releasing it as a public NuGet project. If any changes are made to the feather project the assembly must be replaced manually in the feather-widgets project.

Unit tests covering the COntentBlockModel and the ContentBlockModelCotroller were added.