Fix issue #197 - Index 0 is made transparent, even when it is not the transparent color

Now image_scale and ase_parallelogram_map_standard functions use the image
mask color.
Make "Transparent Color" tooltip smaller in SpriteProperties dialog
Version 1.0.0
Add undo information when the sprite transparent color is modified
Add missing *jguiscale() in Entry and ColorButton widgets
Minor change in sprite_properties.xml (change box -> hbox/vbox/boxfiller)
Fix sprite properties dialog size when jguiscale() = 1 (problem referenced in issue #197)
Use strtol instead of ustrtol in widget_loader.cpp
Fix compilation error in ase_parallelogram_map()