Introduce a ThemeBuilder that simplifies the definition and overriding of style data.

[davetcc]

Is your feature request related to a problem? Please describe. At the moment the raw theme data is too difficult for most to understand, as it exposes complex APIs that take too many parameters to easily understand. The theme builder should allow for the following cases:

• Complete definition of a theme, IE the global theme styling.
• Overriding of the theme styling at both submenu and item level.
• Grid position, IE putting more than one item on a row, or changing the way that an item should be handled.
• Card layout, provide helpers to switch on card layout, and to enable/disable by submenu.

Confirm that the bug is in the embedded library Yes, this is in the library.

Describe the solution you'd like A theme builder as above.

[davetcc]

Although this will be present in 4.2, it will not be used by the designer, it is purely to allow for more testing before switching designer to generate for this class. Consider this experimental, the class may change slightly before the final release.