Update fr-FR.plg_system_less.ini

Add translation for CLIENTSIDE
Merge pull request #17 from lomart/patch-3

Update fr-FR.plg_system_less.ini
'root' is a link to the input file, not the cache file name
Merge pull request #18 from chestersolutions/master

fixed wrong check resulting in compiling altough cache existed:
'root' is a link to the input file, not the cache file name
prepare for release