Add a generic File class.
Fix wrong calls to assert.
Add a tests stub for File.
Fix some compilation errors in File.cpp
Refactor Generator to use File instead of FileUtils.
Update the File class.

 - Add temporary files.
 - Open files automatically on construct.
 - Allow access to the file descriptor.
 - Open files in w+ instead of write only.
 - Close files before removing them.
Migrate Sorting and Chunk to the new File class.
Remove the old FileUtils.
Migrate all test programs.
Add documentation for Sorting and Chunk.
Fix last sorted values not being flushed.
Fix Generator allocation behavior.
Adapt sort parameters.
Update the makefile and write products to bin/