Patch for 'normalize' that crashed with empty set
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 []
Function that exacerbate the extrema of a graph
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.
Patch for the constantLine function

When we wanted to draw a graph with just a constantLine,
it raised a ZeroDivisionError.
This patch corrects this error.
Error with different format of "from" and "until"

When one was defined with "-2d" and the other with "HH:mm_YYYYMMDD"
a error occured because the datetime objects produced weren't comparable.
This patch make them comparable whatever their format
Merge branch 'f_constantline'

* f_constantline:
  Patch for the constantLine function
Merge branch 'f_normalize'

* f_normalize:
  Patch for empty series
  Patch for 'normalize' that crashed with empty set
Merge branch 'f_callback'

* f_callback:
  Use of function sort instead of sorted
  Add a function "callbackToNode"
Merge branch 'f_minmax'

* f_minmax:
  Function to draw an area with the min and max
  Doc and improvement for exacerbate function
  Function that exacerbate the extrema of a graph