Coherent natural dates in taskbrowser columns

[Bertrand Rousseau]

Taskbrowser dates columns should display dates in a natural for specific dates, much like it is done for the due date column in gtg 0.2.1. Columns should be coherent, though (the start date column doesn't behave the same way). Columns should also support other natural dates such as "soon", "later", etc.

As for the implementation, I guess we should use a common object, so that we don't repeat those string everywhere in the code.

[Bertrand Rousseau (bertrand-rousseau)]

See also bugs #516387, #516388 about that issue

[Paul Natsuo Kishimoto (khaeru)]

http://babel.edgewall.org/wiki/Documentation/dates.html#time-delta-formatting (python-pybabel in Ubuntu) — may be helpful.

[Izidor Matušov (izidor)]

I'm not sure what it is goal of this bug (it is quite old), but I think it works now it this way in GTG (you can see now, soon, later/someday in columns). Marking as Fix Committed, feel free to reopen.