Update event: setLegendElemsState accepts object

[Indigo744]

Before, it was only possible to show/hide all legends at once.
But there can be multiple legends on a map (example: http://jsfiddle.net/neveldo/VqwUZ/ or http://jsfiddle.net/neveldo/xd2azoxL). Maybe the user want to show/hide all elements of one of these legends?
Hence the setLegendElemsState is extended to allow the following:

setLegendElemsState = "show"    // will show all legend element (current behavior)
// OR
setLegendElemsState = {
    "areaLegend": "show",        // will show all element in areaLegend
    "plotLegend": "hide",        // will hide all element in plotLegend
    "myLegendClassName": "hide", // will hide all element in myLegendClassName
    ...
},

The user pass the CSS class name of the legend it want to show/hide.

Implements #110 First point.

[neveldo]

I think you could use the already defined variable $self instead of $container here

[Indigo744]

Right! This would be better :-)

What do you think now?

[neveldo]

It's ok for me :)

However, I think that you should provide a new example in the 'advanced' directory for the demo because the 'basic' directory should stand for basic examples that only involve configuration without extra JS code.

[Indigo744]

Right :-) done!

[neveldo]

Thank you, I merge your PR !