Patch for empty series

When a function is called on an empty serie, the function 'normalize'
encoutered an error.
Now it raises a custom error that is tracked by the function 'evaluateTokens'
and returns []
Doc and improvement for exacerbate function

Now, it can have several function in argument
Function to draw an area with the min and max

If a graph has its width smaller than the number of measures, it calls
a consolidate function to know what is the better point to draw.
This function draw the min and max points for each pixel to consolidate
and fill the area between the curves.