Adds the ImageFlip component.
    Adds an ImageFlip field called flip to UiImageBundle.
    Adds flip_x and flip_y fields to ExtractedUiNode.
    Changes extract_uinodes to extract the ImageFlip component values.
    Changes prepare_uinodes to swap the UV coords depending on the values of the ExtractedUiNode's flip_x and flip_y fields.

…flip_x and flip_y fields

…refs to use the texture field instead, fixed game_menu example to work with changed UiImage struct