BUG : deleted the "zlib required" useless in ITK4.cmake

This line was crashing the compilation on Windows.
BUG : working on Windows and Mac too

-deleted the buffer in the DATA ranges to use a sstream, correcting loading issues on Windows and Mac
-add a default value to CMAKE_BUILD_TYPE CACHE for WIN32 to avoid a bug during configuration on Windows
-add verification about existing files for loading, notonly with CLI but drag&Drop and menu loading too