Add a title to a legend

The introduction of HG2 has removed an (undocumented) feature of legends - the ability to easily add titles to them.
This function is to replace/replicate that behaviour.
The function works on both HG1 and HG2.
hTitle = legendTitle ( hLegend, 'your title string' );
The function accepts arg pairs to format/customise the legend.
Function has listeners for the legend changing "Location", "Position" and being Deleted. A listener is also added to the parent figure when it changes size.

This submission is part of the matpigui toolbox (available from www.matpi.com)