TFCGenViewer

Adds an additional button to the "More" tab of the world creation screen, which opens a preview of the world to be created

This preview has several buttons for configuring the preview. In addition to the configuration options there are four other buttons

- Apply: Applies the preview configuration to the review and generates a new image - Save: Saves the configuration to the world creation context, preserving things like continentalness and (if not empty) the seed and returns to the "More" tab - Cancel: Returns to the "More" tab without saving any world configurations - Current Seed: Displays the seed currently being previewed, clicking the button copies the seed to the clipboard