Addition of PERT functionalities to Planner + slip line.

[Gabriel Camby <gabriel camby gmail com>]

Hello Planner developpers,

I'm Gabriel Camby. I started working
on Planner since the beginning of this year. I did a student project on
Planner. This project consisted in adding PERT features and slip line
support in Planner. 

This resulted in a patch, thanks to Maurice van der Pot.

I submitted this patch on Bugzilla adding features from the PERT analysis and from project slippage analysis to Planner. (http://bugzilla.gnome.org/show_bug.cgi?id=585731)


Here are the details:
> This enhancement patch add some functionalities from the PERT analysis and project slippage analysis to Planner.
>
> The PERT functionalities are:
> - addition of a PERT view to Planner containing a task tree and a PERT diagram.
>
> - display of a PERT diagram using automatic configuration of the
> display. Two modes are available "critical tasks on top" and "tasks
> flow".
> - addition of two displayable columns : slack time & free float.
>
> The project slippage analysis functionality is the slip line. It contains:
> - property of displaying the slip line or not in the Gantt view.
> -
> display of a slip line on the Gantt chart when clicking on the header.
> A click in the upper part displays a slip line at the choosen date with
> a thick line. A click in the lower part displays a thin line.
>
> Note: the print parts for those additions are not implemented.



Can it be merged in Planner or in a branch?
I'll be glad if you tell me what you think of it.

Regards,
Gabriel Camby.