FIX: Load tkpng to show png directly from thumbnails.

this makes instant thumbnail show from directory. If tkpng
fails to load fallback to previous behavior and render gif
FIX #66 : Allow negative values in watermark offset
FIX #69 : IF final size bigger than svg 100% size, render bigger.

Small fix on i8N strings
Fix load order for tkDND to work. (It has to load after widgets are
created)