qa_tests/_utils:

Added base QA test class method for testing with variable precision.
qa_tests/hazard/event_based/case_2:

Added event based QA test, case 2.
qa_tests/hazard/event_based/case_4:

Adapted case 4 for the event-based calculator.
qa_tests/hazard/event_based/case_8:

Initial draft of case_8 for the event-based calculator.
qa_tests/hazard/event_based:

Fixed imports.