Draft: Implement dynamic Settings Manager UI

Very early WIP. I originally wanted the settings user interface to be dynamic. You should be able to register a setting with the Settings Manager from anywhere in the code and the Settings Manager should be able to create a settings UI for it. At least that was the goal. I think it's doable for simple settings (booleans, numerical values, strings) but maybe not for things that require entire data structures (for instance, manually entered device detection). I want to have a try at creating at least a basic settings system.

The goal is to autogenerate the UI, for example:

from a json object that can be created anywhere where you want to add settings like so:

    json                ui_settings_proto;

    ui_settings_proto["numerical_labels"]["name"] = "Numerical Labels";
    ui_settings_proto["numerical_labels"]["type"] = "boolean";

    ui_settings_proto["disable_key_expansion"]["name"] = "Disable Key Expansion";
    ui_settings_proto["disable_key_expansion"]["type"] = "boolean";

    ui_settings_proto["greyscale_tray_icon"]["name"] = "Greyscale Tray Icon";
    ui_settings_proto["greyscale_tray_icon"]["type"] = "boolean";

    settings_manager->RegisterSettingsPrototype(ui_string, ui_settings_proto);