Sequencer "event-like" methods

[TomKovac]

Sequencer should have "event-like" methods
OnStepDone(step: IStep),
OnStepError(step: IStep), and
OnStepStart(step2start: IStep, previousStep: IStep).

Two additional methods to complete the current step and move forwards should be added,
MoveNextWhen(cond: BOOL) and
MoveNextWithErrorWhen(cond: BOOL).

Completing the current step should be done as follows:

1.) with calling MoveNext() method- should complete the current step with a Done flag and trigger the OnStepDone(step := currentStep) method.
2.) with calling MoveNextWhen(cond := TRUE) method- should complete the current step with a Done flag and trigger the OnStepDone(step := currentStep) method.
3.) with calling MoveNextWithErrorWhen(cond := TRUE) method- should complete the current step with an Error flag and trigger the OnStepError(step := currentStep) method.

OnStepStart(step2start, previousStep) should be triggered when the step2start is triggered.