fstream and iostream clean-up
Summary
There are a lot of useless include of iostream and fstream in OTB. This MR tries to reduce those include to their bare minimum.
Rationale
fstream and iostream are huge headers that take a lot of time to parse when compiling. Removing them might improve build time.
Implementation Details
I just removed all includes of iostream and fstream and gradually put them back where they where needed. If you look at the diff, you will see that many of them were actually useless.
Copyright
The copyright owner is CNES and has signed the ORFEO ToolBox Contributor License Agreement.
***Check before merging:*** - All discussions are resolved - At least 2