Move a "before filter" to 'filters' file
Set locale in a "before filter", commit 1/2
Set locale in a "before filter", commit 2/2:

normalise indentation.
Use URLs with locale for downloading
Use more general language selection links:

do not use the value of 'page', use 'request.path_info' directly.
Use single quotes for non-interpolating strings
Use strings instead of symbols to name pages