Most short sentences and mails translated to french
some more done in 'welcome'
signup, signup mail and conditions done, plus some changes
add missing comma in about
Correct typo and incomplete parts.
typo correction
folder name requires lower case
Merge updates from cslinmiso/zh-TW
Merge updates from nicolasbd/french
Merge branch zh-tw-cslinmiso
Minor fr updates, like &nbsp; for spaces ...

... before puncutations.
Add fr translation for "Switch language"
Add zh-tw translation for "Switch language"