UI changes in voting tool before release

Part of #975

What does this MR do?

These are some ideas for hints and links, which I hope are sufficient if people need to find help and still don't spam the page too much. If you want to add or change something here, please feel free to do so.

Some small UI changes:

• do not select any options by default in the "thumb" voting (picture 1)
• add hints that the order of options is random (pictures 1 and 2)
• relabel the "average" column in the results to "sum" because it's not an average (pictures 3 and 4)
• add a link to the wiki page to the poll list table, the voting form, and the "new poll" form (pictures 5 to 7)

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How confident are you it won't break things if deployed?

Quite sure, these are only UI changes

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• set a "for:" label to indicate who will be affected by this change
• use "state:" labels to track this MR's state until it was beta tested
• added an entry to CHANGELOG.md
• add a short text that can be used in the release notes
• Once your MR has been merged, you are responsible to create a testing issue in Beta Testing Repo:
  • Consider writing a detailed description in German.
  • Describe in a few sentences, what should be tested from a user perspective.
  • Also mention different settings (e.g. different browsers, roles, ...). how this change can be tested.
  • Be aware, that also non technical people should understand.