Dataset support

[didikunz]

Support for CasparCG datasets is missing from Superconductor. What is an important feature of Caspar, when it comes to sports or stock market data and the like.

The implementation can be very similar to how it's done in the official client: A checkbox "Use Dataset" and a text-box with the name of the dataset.

A list of avalable datasets could be presented to the user somehow, but that is not so important at the first place an could be added later.