Visual indicator of any minor(!) problems with data that may affect validity of PCA analysis

In some cases, numerical algorithms can fail in difficult to detect ways. The results may still be meaningful, but due to the failure of certain assumptions, perhaps not 100% valid.

This is the case with JAL-1454 - lack of convergence of the PCA results in a not-quite diagonal matrix, and thus an imperfect PCA embedding of the original sequence similarity matrix. If warnings are generated that indicate that the algorithm did not converge, then a visual indicator should be shown in the viewer to inform the user of that fact.