fr.po, fixed gammar & spelling

I fixed the fr.po file which had numerous grammar and spelling issues, I suppose the translator wasn't a native speaker.

Anyway should I submit it as a patch or is the new file (attached) good enough ?

On a side note, if someone knows how to get visitors (i.e. not logged in) to get the French version of that form instead of the default English... (apart from the obvious messing around with po files). I did disable English but it didn't change anything...