Transform are now instanciate one time (first use). This modification
allow to load on memory GAN model one time given a huge gain on
multiply computation (tested on sample_dir give me 162 seconds to 92 seconds (amd FX feel bad)).
This modification break cpu multiprocessing support until a multiprocessing manager
is implement to avoid race condition. Also added --disable-persistent-gan to
disable in memory persitent gan for low memory environnement.
* Change all the logic of the phases to more flexiblility
* Add rescale/resize/overlay as phases (the same level that gan/opencv
* Add more comments everywhere
* Modify Configuration(Options) Class to be more general (args, checkpoints
location and multingthread configuration are now acccesble from it)
* Add logging with debug option (-d, --debug)
* No fonctionnilaty change