Test is saivng a file

Test now saves a sample file, next thign to do is make sure the file is formatted right
Load hasn't had anyhting happen yet.

Refs #5344
test_LoadNexus() completed and test_SaveNexus() tidied

The unit test for WorkspaceHistory now tests that LoadNexus() loads everyhitng properly, and SaveNexus() saves everything properly.

test_SaveNexus() has also been tided since last commit.

Refs #5344
Merge branch 'feature/5344_WorkspaceHistoryTest_Additions' into develop