Enhance feature setLegendElemsState: be able to tell which kind of elements we want to hide or show : 'areas', 'plots' or 'links', and for which interval of values (if the elements are associated to one or more value(s), it has to be compatible with multiple valued elements). For example : "I want to show only the plots which the associated value is between 1000 and 1200) :
{ 'plot' : {'min': 1000, 'max': 1200},  'area' : {'min': 10, 'max': 20}}
{ 'plot' : 'all'} 
{ 'plot' : 'none'}
(...)
It would allow to play with some sliders in order to allow users to select ranges of values for which we want to show the elements.