This function aims to simplify the creation of a legend for scatter plots.
The function will plot a legend on current axis with the right
markersize proportion.
NB. From version 1.0.5 is added the compatibility with previous MATLAB
version.
-------------------------------------------- INPUTS
- TextCell: a cell array containing the legend-entry text.
WARNING: THE FIRST CELL IS THE TITLE !!!
- SizeDim: the ''MarkerSize'' dimension for each entry.
WARNING: length(SizeDim)==length(TextCell)-1 !!!

- Factor: normaling factor for enlarge the marker size in
a linear way. (MarkerSize*sqrt(Factor)

- LinSpec: specify the marker-string.

-------------------------------------------- EXAMPLE
Factor=1.5;
A=[1,1,1;
2,2,2;
3,3,3;
4,4,4;
5,5,5;
6,6,6;
7,7,7;
8,8,8;
9,9,9;
10,10,10];

sh=scatter(A(:,1),A(:,2),(A(:,3).^2)*Factor,'ok');
%scattersize==MarkerSize*sqrt(Factor)pt)
leg=LEGENDSCATTER({'SIZE','1','2','3','4','5', ...
'6','7','8','9','10'},[1:1:10],Factor,'ok');
leg.Location='NorthWest'; axis([0,11,0,11])

-------------------------------------------- INFO
VERSION:1.0.5
AUTHOR: Matteo Bagagli - ETH-Zurich // Oct. 2016
MAIL: matteo.bagagli@erdw.ethz.ch