Start i18n.
Start i18n.

Lots of i18n changes (squashed commit).
Now *.mo installs when doing scons install.

achadwick/libmypaint,b3sigma/libmypaint,b3sigma/libmypaint,achadwick/libmypaint,achadwick/libmypaint,achadwick/libmypaint,b3sigma/libmypaint