Now we can specify a printf filename format and the save is made by PIL.
The image is build from array in main thread (avoid overhead of sending the
array through a pipe) and then saved by a Pool.

Add a correction to ensure that fractdim score is in [0..1]. The new
score in given by 1 - (1/((x+1)**4)) with x the old factdim score (between
[0..2] or [0..4] ).

Now the collect interval is incremented at each dirvar update

By compiling code on the fly and falling back to std method for jumps

Turmit stack size was 0 sometimes
Mutator sometimes delete leading to empty expressions

Now steps count evolve given the try number from 100% to 33%

first turmit that looks nice :D

A world (World) is a place where turmit can run (LivingTurmit) and has
methods to determine its fractam dimention and to save a representing image

L'essentiel du main sera déplacé dans un module