Refactoring JavaFX GUI Code, Part 2: Using and Binding Properties

This continues my series on refactoring a simple JavaFX application. In the first part of the series, I used functional decomposition to improve the quality of the code. However, functional decomposition could not solve a particular category of problem: the fact that there's an implicit dependency on the idea "querying is enabled", but that concept has no explicit representation in the code. By using and binding JavaFX Properties, we end up with an even better design for the application source code.