Simple priority scheduling

[Terry Barnaby <terry beam ltd uk>]

Hi, I have been using planner on and off for a few years now for some 
projects. Its not ideal but works ok for us. The biggest issue though 
has been the lack of some form of automatic scheduling of tasks that 
share the same resource.
There was the --enable-simple-priority-scheduling build option but
this did not seem to do much if anything.
Anyway, we wanted to have some basic priority scheduling for a project
and after looking around at alternative programs decided to modify
planner a bit.

So we have implemented a basic priority scheduler, enabled with the
--enable-simple-priority-scheduling build option. What this does
is:

1. Has a "scheduling" checkbox in the project dialog to enable
   the feature. This is saved to/restored from the xml project file.

2. When enabled if there is any degree of clash between two tasks
   that use the same resource the task with the lowest priority
   and its dependants is/are moved in time to be after the task with
   the higher priority.

3. If the clashing tasks have the same priority, the earliest task
   in the list of tasks (nearer the top) are deemed to have higher
   priority than the ones below.

At the moment I use a simple toggle button to enable, but an integer
is stored in the xml file to enable it so it would be possible to
extend this with various simple algorithms.

I can provide a patch for this, but I don't have much time to really
polish it and update the main sources. Some things may need to
be changed (for example I have modified the mrproject-0.6.dtd file
it may be better to have an updated version dtd file etc).

I'm not sure if anyone is actively maintaining the code and/or
thinks this patch would be a good idea and would like to take the
patch and update the code ?

Terry