Fixes integration with EPL/Spot type transformers.

There was a problem with an algebraic loop when the *output*
was used non-delayed. Still not sure why this is but putting
a simple delay on the output port solves the issue.

Tests with ObjectStab integration follows.
Clean up of the diagram layer.
Add start value for tappos_offset
Adds test that is based on ObjectStab lib, also delay the real output.

The tests with ObjectStab[1] has shown that also the real out put
needs to get delayed.
Strange...

[1] https://github.com/modelica-3rdparty/ObjectStab