Bug 126839 [DataBinding] IObservable refactoring
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/internal/provisional/databinding/converterfunction/TwoWayConversionFunction.java
private IConversionFunction targetToModel;
	private IConversionFunction modelToTarget;
	
	/**
	 * Constructs a Converter that looks up its target to model and model to target methods
	 * in the ConversionFunctionRegistry.
	 * 
	 * @param targetType The target type Class
	 * @param modelType The model type Class
	 */
	public TwoWayConversionFunction(Class targetType, Class modelType) {
		targetToModel = ConversionFunctionRegistry.get(targetType, modelType);
		modelToTarget = ConversionFunctionRegistry.get(modelType, targetType);
	}
	
	/**
	 * Constructs a two-way converter function by supplying two one-way