Bugfixes in voting

- When comparing identity properties, if only one property is null, they
are now considered to match if the name and salt are the same.
- Don't check the signatures of the verifiers on newly accepted
identities (clock desynchronization between client and server can cause
false negatives)
Issue #1038: More work on contest visualization

Specifically, account for the contest and decision types in the
instructions.
Issue #1038: Refine contest visualization for vote one and vote yes/no