Add filters to poll single votes

[bastianjoel]

resolves #3899

[Elblinator]

The filters have to be hidden in a non-nominal vote

The filters are currently displayed in ballots and topic polls as well but they are not working
They either have to work there as well or they have to hidden

please change my crude "cat.value" = "Y", "N", "A", to the actual words

[emanuelschuetze]

• Rename "Weighted votes" to "Valid votes"
• Hide line "Ballot cast: ..." if vote weight is disabled / not used in poll.
• Line "Weighted votes": add abstain to total, and add abstain value (without percent!)
• Line "Ballot cast": add abstain value