[picnic] Refactored UserSessionIf
[picnic] Interface name ends with "If"
[picnic] More testable code for user model. Renamed rucksack interface
[picnic] UserModel -> userModel
[picnic] todo
[picnic-rd] add src/img/somerights20.png
[picnic] Fix tests
Merge branch 'userIF'

* userIF:
  [picnic] Fix tests
  [picnic-rd] add src/img/somerights20.png
  [picnic] todo
  [picnic] UserModel -> userModel
  [picnic] More testable code for user model. Renamed rucksack interface
  [picnic] Interface name ends with "If"
  [picnic] Refactored UserSessionIf