use file in english if translated one is not found
oops, forgot to update the po4a file during the recent package reorgs
retranslate everything of pancakes exercises
crap, the rank0 is the topmost pancake, not the bottom one
Fix constructors

- insist on mixing the random plate, even if order can come out of
  random, this is too disturbing to normal beings
- Add a constructor that takes a given order as parameter
add a new exercise on pancake sorting, much more challenging
display graphically which pancakes are already sorted
Kill InvalidPancakeRank and use InvalidParameterException instead

Nobody wants to survive this exception anyway
DoWhile is not an application of LoopFor
dont let the editor die on an exception when the user is stupid
allow to use custom colors in the map editor