Add missing comma in preference.json

French translation was not usable because the file preferences.json was invalid.
Add french translation

Added french in locales.json
Added contributors for french translation
Added french in the list of supported languages
Shorten "smarty-pants" translation to avoid line wrap
Add missing comma in preference.json

French translation was not usable because the file preferences.json was invalid.
Add french translation

Added french in locales.json
Added contributors for french translation
Added french in the list of supported languages
Shorten "smarty-pants" translation to avoid line wrap
Merge remote-tracking branch 'origin/master'
french translation for "tasklist"
Merge pull request #52 from daniel-menard/master

Corrected french translation