X and Y coordinates of ternary plotting area

- direction
(optional) Integer specifying the direction that the current ternary plot should point: 1, up; 2, right; 3, down; 4, left.

`TernaryXRange()`

and `TernaryYRange()`

return the minimum and
maximum X or Y coordinate of the area in which a ternary plot is drawn,
oriented in the specified direction.
Because the plotting area is a square, the triangle of the ternary plot
will not occupy the full range in one direction.
Assumes that the defaults have not been overwritten by specifying `xlim`

or
`ylim`

.

`TernaryYRange()`

: Returns the minimum and maximum Y coordinate for a ternary plot in the specified direction.

Other plot limits:
`OutsidePlot()`