Added the possibility to add gaussian noise on a radar image.

      * src/main.cc: Here.
      * src/ImwHelper.cc: From ProjIMA, helper to handle radar files.
      * src/ImwHelper.hh: From ProjIMA, helper to handle radar files.
      * CMakeLists.txt: Added ImwHelper.cc to compile chain.
Added the possibility to add rayleigh noise on a radar image.

      * src/main.cc: Here.