It returns a dataframes
roundPlotMark(roundness, x, y, dfMarkColorInternal, listOfdfMarkPosSq,
chrWidth, yfactor, n2, lwd.chr)
roundness of vertices <
x component of polygon
y component of polygon
colors for marks
list of df. of mark pos.
width of chr.
y distortion based on canvas proportion
numeric, to define vertices of rounded portions
thick of border line
plot