baseMixin.filterPrinter defaults to dc.printers.filters plural, not singular

The text is correct, but it references the wrong class.

> By default dc charts use a default filter printer `dc.printers.filter` that provides simple printing support for both single value and ranged filters.

That's `dc.printers.filters`; also below in the table.

Also it should link to the documentation for the class. And it should provide an example, for the function signature.