Format colgroups

[Jolanrensen]

Fixes #1356

Now you can actually do this:

df
    .format().with { background(white) }
    .format { age }.with { background(blue) and textColor(white) }
    .format { name }.with { background(green) }
    .format { name.firstName }.with { italic and underline }
    .format { name.colsOf<String>() }.where { it.startsWith("C") }.with { background(red) }

Note, this does not solve #982 yet

[koperagen]

This now formats both firstName and lastName?
df.format { name }.with { italic and underline }
If so, add "Columns inherit formatting from containing column group" or "Formatting a ColumnGroup applies to all its children (or nested columns)"

[Jolanrensen]

This now formats both firstName and lastName? df.format { name }.with { italic and underline } If so, add "Columns inherit formatting from containing column group" or "Formatting a ColumnGroup applies to all its children (or nested columns)"

I shall expand the kdocs a bit :)

[AndreiKingsley]

Nice! But yeah, need to describe behavior.

[Jolanrensen]

I'll also update the documentation site btw, I forgot about that, then I'll merge :)