* It's a good practice to put the main target on top, since it's the
  first one that is called when calling just "make". That's why
  "resources", "binaries" and "gettext" were moved up in their
  Makefile's.
* Added a "clean" target for each subdirectories so that they are a bit
  more autonomous.
* Using "&&" instead of ";" when changing directory because if a
  directory name is changed, we get into an infinite loop.