Badges, poll and french Translation

New Badges system
New string in the poll plugin + change the term "poll option"
Re-add some empty strings (like notifications.title)
And updates
Poll - Topic Term

Use topic instead of thread to keep the same term for the user.
Dutch translation updated
Dutch translation updated
Merge pull request #2142 from sanderdatema/patch-5

Dutch translation updated
Merge pull request #2135 from Onaldanm/poll-badge-fr

Translation: Badges, poll and french updates
Merge pull request #2134 from Onaldanm/patch-1

Poll - Topic Term