Add summary statistics

[paddymul]

Summary stats

Add a base no-arg summary statistics function, that can operate on either the input DataFrame or transformed DataFrame. enable a toggle via the UI

Try to limit display to 5 rows

Column level features

for text columns

display number of discrete values vs total number of rows
If there are only a couple of discrete values show those values

If there are a limited number of outliers, show them

for integer and float columns

Show a histogram sparkline
list quartiles
medina, mean, stddev