refresh a bit a documentation about the components of the main window
move to the end of the po file a documentation file that is not very visible in the interface
kill the lesson chooser. Long time no use, now that we have the ChooseLectureDialog
no need to translate the backtracking lesson for now: far from functionnal and stalled
reorder the stuff to translate in the hope that people first translate important stuff
Relaunch po4a after the recent content reordering. Don't commit pt_BR to not conflict with Fred
adapt french translation to recent english changes in the MainWindow documentation