Backdrop will now discover <theme>.settings.json configuration files in a theme config folder

Backdrop will now discover any theme settings saved in a config folder in a theme in the format of <theme_name>.settings.json.

The settings file should be registered in hook_config_info() placed in a template.php in the theme root directory.

Note that this provides an alternative for how themes save data to the active configuration. The other methods include syncing from the <theme_name>.info file during enabling, or saving the theme's settings form.

This new settings file can be used as an alternative to info file settings such as settings[]=xxx.