[Ml-yokadi] Permanent keyword filter

[Sébastien Renard]

Hello,

I don't remember who ask for that feature, but it's done ;-). It now possible 
to add permanent keyword filter.

t_filter !@home will filter all further t_list call by removing tasks that have 
the 'home' keyword.
The prompt notify the current filter (if any) or default to standard 'yokadi 
>'.

You can define multiple keyword filter with value and negative (!) prefix.

Exemple : 
yokadi> t_filter @_severity=3
y @_severity=3> t_list

                                            pysql (dev)
ID |Title                                                |U  |S|Age     |Due 
date
---------------------------------------------------------------------------------------------------
150|datamodel does not handle table with accentuated name|17 |N|48w, 4d |
y @_severity=3>
y @_severity=3> t_filter none
yokadi>


Hope you like it ! It needs some more stuff : completion, check for keyword 
existence.... and unit test of course ;-).

-- 
Sébastien