Remove external dependencies from ISIS3 test data
Most of our unit and app tests that use a cube with a DEM require data outside the
$ISIS3TESTDATA areas, since the DEMs are usually located somewhere else. I noticed that this caused some trouble when I first went remote because I had to mock up all the DEM's full directory paths referenced in test cubes locally for the tests to run. All of our test data should be isolated to our data areas and should not have external dependencies. This is important both because it will help facilitate testing for external devs and also there's no guarantee that the DEM files will never move or be renamed. Right now, doing so would cause many of our nightly tests to fail.
As part of this, DEMs referenced in test data should be copied to the $ISIS3DATA or $ISIS3TESTDATA areas and all of these test cubes will need to be re-spiceinited with the newly moved DEMs.