- added three additional zoom-levels and icon-sizes (160px, 192px and
256px)
- added usage of "large" thumbnails (max 256px x 256px)
- automatically use large thumbnails for icon-size > 128px
- renamed zoom-levels, usage of percentage values
- renamed icon-size values, count in pixels
- support for old naming

- fixed conflict after cherry-pick from
master (thunar/thunar-icon-factory.c)