Added UseCaseScenario3 for Demo3a Test

Signed-off-by: makulik <g-makulik@t-online.de>
Merge branch 'master' of https://github.com/makulik/sttcl.git

* 'master' of https://github.com/makulik/sttcl.git:
  Added UML diagram images
  Added Demo3 Use Case Scenario test descriptions
Added Demo3 Use Case Tests