Clean theme still has "Simple" all through the docs.

Comments and docs still contain "Simple":
>> grep -r imple clean
clean/config.php: * Moodle's Simple theme, an example of how to make a Bootstrap theme
clean/layout/general.php: * Moodle's Simple theme, an example of how to make a Bootstrap theme
clean/layout/general.php: * @package theme_simple
clean/lib.php: * Moodle's Simple theme, an example of how to make a Bootstrap theme
clean/settings.php: * Moodle's Simple theme, an example of how to make a Bootstrap theme
clean/style/custom.css:/* Simple Custom CSS
clean/version.php: * Moodle's Simple theme, an example of how to make a Bootstrap theme