Nova translations for tool lines

[alex-osborn]

Great work with the package.

Currently the Nova tool label can be customised with config('novapage.label').

However, other strings in the tool are hard-coded and cannot be updated.

Most of these could be run through translations to allow this, such as changing Whitecube\NovaPage\Pages\Resource::singularLabel()

    /**
     * Get the displayable singular label of the resource.
     *
     * @return string
     */
    public static function singularLabel()
    {
        return 'nova-page';
    }

    /**
     * Get the displayable singular label of the resource.
     *
     * @return string
     */
    public static function singularLabel()
    {
        return __('nova-page');
    }