Graphs: smooth network bursting (enhansment)

[acoul]

the following patch helped a lot in smoothing the graphs on network bursts:

- "--slope-mode --alt-autoscale -u 0 -l 0 --imgformat=PNG --base=1000 --height=$height --width=$width " .
+ "--logarithmic --slope-mode --alt-autoscale -u 0 --imgformat=PNG --base=1000 --height=$height --width=$width " .

it may be nice to have this as an option in the config file.

[acoul]

while this is great for the spikes issue, we loose the negative display.

There is this an interesting blog about using trends to fight the spike issue.

I've also bumped into this: negative logarithms

an example of the issue and the same graph with logarithmic scale.