Merge branch 'story40-zoom' into 'master'

40. [V] As Caleb or Gemma I'd like to zoom the view to follow a boat (my boat) around the course (revised).

Note: in this story we will select a boat and zoom the view to place the boat at the center of a display that shows only the boat's immediate surrounds. The default option will be to zoom on the player's boat.

Acceptance criteria:
- Any particular boat can be chosen (at any time during the race.)  
- When a boat is selected for zooming, the view should change to show the boat at the center, with the scale of the view increased.
- The view should remain this way until the boat is unselected, at which point it should revert to the usual display.
- Other information (e.g., the position list) may be removed from the zoomed view.
- Zoomed view follows selected boat as a third person mode
- There must be a keyboard option to zoom in on the player's boat_
- The zoom amount can be fixed (jump between zoom in and zoom out) or scrollable (like control-mousewheel scrolling.)

See merge request !38

racevisionGame/src/main/resources/visualiser/scenes/race.fxml

@@ -22,7 +22,7 @@
 <?import javafx.scene.layout.StackPane?>
 <?import javafx.scene.text.Font?>
 
-<SplitPane fx:id="race" dividerPositions="1.0" prefHeight="431.0" prefWidth="610.0" visible="false" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0" xmlns="http://javafx.com/javafx/8.0.65" xmlns:fx="http://javafx.com/fxml/1" fx:controller="visualiser.Controllers.RaceController">
+<SplitPane fx:id="racePane" dividerPositions="1.0" prefHeight="431.0" prefWidth="610.0" visible="false" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0" xmlns="http://javafx.com/javafx/8.0.65" xmlns:fx="http://javafx.com/fxml/1" fx:controller="visualiser.Controllers.RaceController">
     <items>
         <GridPane fx:id="canvasBase">
             <columnConstraints>