Refactor js test runner error handling

- auraErrorsExpectedDuringInit is used to declare expected errors a js test
  encounters during test init
- auraWarningsExpectedDuringInit for expected warnings
- Test.expectAuraError used for expected errors during test execution
  only, not test initialization
- Test.expectAuraWarning for expected warnings
- Test will fail on any errors not declared as expected or if an
  expected error is not encountered

@bug W-2142879@
@rev gtorres@
Merging origin/tbliss/master-pending-test-fail-better-handling into master