more efficient trap against bug in the demo code of pancake exercices

I saw cases where one of the algorithms failed to sort the array, but
I didn't get enough information to fix it.
add a rule to test whether we're catched by https://code.google.com/p/gettext-commons/issues/detail?id=55
Retranslate all missions back to 100%
fix all formating errors in the translations of the engine
add a comment in the ant file explaining what's going on here