Bug fix - add unit test for TermSetImport(), the fix by reloading set of...

Thanks to Jim Duncan for notifying me of the error; it also teaches me that I should add unit tests for new functionality.

* Added unit test for ImportTermSet(); the test uses the sample file from the Term Store management UI.
* Wrapped exceptions to also report the line number causing the problem.
* Fix bug with multiple levels of term set not working correctly.
* Added example logging to test App.config.sample (this will direct logging output to the console, which will show up in the Output section of the test).