* Add a default dialog and handler class.
* Move the main parts of the service from the base plugin to the kernel.
* Introduce a severity enum since using int "codes" is flawed and we do
  not use underlying eclipse methods like the logging methods in the
  LoggingUtils class.

Issue-Ref: 3574
Issue-Url: https://af3-developer.fortiss.org/issues/3574


Signed-off-by: Alexander Diewald <diewald@fortiss.org>