Formatting features

1.  \null [string] - Show or set NULL representation
2.  \f [string] Show or set field separator
3.  \t [on|off] Toggle or set tuple only output
4.  \a [on|off] Toggle or set aligned output
5.  rightmost column is no longer padded
Tests added and updated

No args toggles, right? Perhaps "Toggle or set tuple only output"  would be clearer. Dittot alignment below.