Add user-defined color theme support to TUI #20
Description
While the TUI should offer some basic predefined themes, it would be nice to offer a way for the user to customize it.
This would likely be in the form of a JSON file where the user may define a list of schemes matching one of the application states (i.e. normal, lock, fault). Additionally, each scheme may define a base which to base that state's style on (i.e. one of the preconfigured schemes built-into the app). Finally, the user may define any of the ColorScheme properties to override for a given state's scheme.
Complications, it is not clear how easy it will be to deserialize such a payload to update the SpectreConsole's Style and Color classes. This might have to be done in a brute force way, but perhaps some programmatic processing using reflection could be developed to ease this maintenance burden.