The server's console in Eclipse shows many errors after I clicked the "Play" button in the Server view in Eclipse to start Worklight Server.
The errors from the Console view can be viewed here: paste2
This most likley happens due to using Java 1.8 (see IBM Worklight 6.1 - Error TRAS0033E).
Downgrade to either 1.6 or 1.7 and make sure to setup Eclipse to use the JRE of 1.6 or 1.7.