[Ml-yokadi] Increasing urgency with time

[Sébastien Renard]

Hello,

Yokadi is happy to have separate urgency and due notion. But, I think it could 
be smart to take time into account in urgency definition.

How about increasing urgency accoring to task age ?

We could for exemple compute urgency as : 
base_urgency + number of days since creation.

I have a working patch but I would like to have your opinion before merging.

-- 
Sébastien