UX: Paste large models into a subprocess

In Klarify we try to enforce BPMN rules wherever possible in order to ensure standardization. For example, BPMN rules don't support multiple start events in a subprocess, nor do embedded and transaction subprocesses support start event markers. Having said that, this rule often conflicts with other actions process modellers are trying to perform, like pasting a process model into an existing subprocess. In these cases, Klarify would not permit deleting the start event before pasting (must contain at least one start event), nor would it permit pasting the process model which contained another start event (must not contain more than one start event). We're now allowing modellers to delete the start event from a subproces or paste more than one start event. Rather than prohibiting these actions we now display a warning notice instead.