Simplify UI

[florian-str]

User Story: As a user, I want the UI of Liquid to be less complex so that the friction of using it is lower.

In a recent spike (#239) we have explored how the UI should be modified to make the application easier to use.

• [ ] Remove Stop Server from launch screen
• [ ] Add a new window for poll management
  • [ ] List existing polls
  • [ ] Create polls
  • [ ] Delete polls from overview page
  • [ ] integrate poll drafts
  • [ ] stop server