Show column types

[pdeffebach]

Just like a DataFrame shows column types, it would be great if TableView did as well.

Stata, for example, has different colors for different types. Strings are in red, categorical variables are in blue, everything else in black. This makes it super easy to figure out what's going on in your data set.

[pfitzseb]

Column types are displayed as tooltips when hovering over the header.