Addition of Testing Functionality

Added updates to the mrvTest test suite, as well as a brand new test function 'test_niftiStruct' that tests a lot of the functionality in niftiStruct (without using a dataset, for now). This is a major update to coincide with the major update in vistasoft. This release will need to be timed together as vistasoft and vistadata as the functionality here is dependent on those.

I will leave this pull request open during the break if anyone wants to take a look at it. I hope to complete this pull upon my return and when we update to the new version.