+tck testing for test skipping and fix in spec104 skipping regression

* spec104 must be skipped, and not fail for no given error publisher
* added verification that spec112 is SKIPPED as expected, for no err-pub
* missing skip exception in optionalActivePublisherTest

* We uncovered that the 104 spec validation would not be properly skipped due to an regression - this is now fixed. To avoid such problems in the future, optional tests are now covered with tests that check that they SKIP as expected.
better messages for implementers when they see a skipped error publisher test, and want to implement it - now they know what to impl.