Redudant Code--Explore Tab Sets

[neilhatfield]

The usage of tabset panels has created a lot of redundant code in this app. This is especially true in the Explore section. I would like for us to move away from tab panels for different models to a layout more focused on the assumptions themselves. Within each assumption's page, we can list what models they apply to. This would allow us to reduce 5 separate iterations of QQ plots for checking the Gaussian/normal residual assumption to just one instance.