Add XYShapeAnnotation support

[matoos32]

No description provided.

[matoos32]

This one is hitting a road block. For gapless charts we need to somehow map the java.awt.Shape's time coordinate to x-coordinates as indices in time arrays for use in NumberAxis, but Shape is an interface and concrete classes can have any number of x-coordinates passed-in and in any number of ways. The interface provides no means to get shape coordinates polymorphically. So it requires specific logic for 30+ different known implementing classes. See https://docs.oracle.com/javase/8/docs/api/java/awt/Shape.html.

That is a big effort possibly warranting a ticket for each and with high maintenance burden. It's also unclear how much demand there is for these capabilities at all in the builder framework.

So I'm going to merge the implementation for DateAxis ("with gap") charts where in that context it's a general solution for shape annotations.

The implementation for NumberAxis ("gapless") will be left as unsupported but as a TODO to be figured out if there's enough community demand for it. Support for specific Shapes can be added on a case-by-case basis while thinking about how to add them all in.

I know this is not ideal but it's the best I can do within my time constraints.