CODE resize small optimizations to sizeTreeToggle
FIX #68 : Add step modifiers to size spinboxes

Normal 10x
Hold shift 1x
Hold Shift+Alt 100x

Another possibility could be to hold Control to cicle trough pre-
defined sizes.
FIX #54 : set ratio based on wxh contents.

Small GUI improvements on ratio and wxh
ADD internationalization markers
Migration to translation support
ADD: default.pot and spanish draft translation