Asynchronous entailment checks for saved testcases

When a new saved test case is created, asynchronously check whether positive TC are entailed in the ontology and negative TC are not entailed in the ontology.

Mark the TC with green for positive check, otherwise mark with red background. As long as the check is beeing done reflect the ongoing check with an appropriate icon.

Check on creation, opening, changing and reloading of the ontology. Use of OntologyChangeListener.