Support maxWidth in tooltip theme

[klondikedragon]

While a concise tooltip is better than a very long tooltip, a very long tooltip that wraps into several lines in a reasonable width box is preferable to a long tooltip that fills the entire width of the screen.

The tooltip theme should provide control to limit the max width of a tooltip, wrapping text onto multiple lines as needed instead of expanding horizontally to fill all available space.

This is simple to implement. A PR will be submitted shortly.