Extend (regression) tests

In view of upcoming modifications - for instance implementing the LOFAR HBA (#55 (closed)) and LBA responses more efficiently - a couple of (regression) tests are added, just to avoid that later modifications unintentionally break down functionalities.

This issue covers at least the following regression tests:

• Test the response for a LOFAR LBA measurement set
• Test the Station::ComputeElementResponse method for HBA