eikos_legend: Create eikosogram legend
In eikosograms: The Picture of Probability

Eikos helper function used to create legend.

1 2	eikos_legend(labels, title = NULL, yname_size = 12, yvals_size = 12, col, margin = unit(2, "points"), lcol = "black")

`labels`	labels to be included in legend
`title`	if non-NULL a string to give as the legend title
`yname_size`	font size of vertical axis names (in points)
`yvals_size`	font size of labels for values of y variable (in points)
`col`	colours od
`margin`	unit specifying margin between legend entries
`lcol`	line colour