Urls reconsideration

[Ducasse]

• check URLs case: when generating a website links are casesensitive and
  -- a checker that verifies that there is no file with the same name but different cases (on mac this is not possible) but on linux or windows it is
  -- we can make sure that the HTML writer outputs lowercase files with lower case links.

• can we output files (and not url) with space.
  right now urls are encoded.