updated gnucash's french translation : fr.po

[Yannick LE NY]

Hello,

I send you the updated gnucash's french translation : fr.po.
This file is for Gnucash 2.1.5 and include all the strings from the 
latest subversion gnucash trunk.

It was a long time ago when I made my latest translation for Gnucash : 2001.
In 1998, I was the first translator for Xacc , before Xacc was renamed 
in Gnucash.
And in 1998, there was only one developper : Linas Veptas.
But now there are more developpers.

Best Regards.

Yannick.