Expand zoom buttons functionality

[Indigo744]

Implements #166 and add some customization to zoom buttons !

The default options now looks like this: for each buttons, a cssClass, content and title is provided.

defaultOptions: {
    map: {
        zoom: {
            /* ... */
            /* removed zoomIncssClass & zoomOutcssClass */
            /* ... */
            buttons: {
                "reset": {
                    cssClass: "zoomButton zoomReset",
                    content: "•", // bullet sign
                    title: "Reset zoom"
                },
                "in": {
                    cssClass: "zoomButton zoomIn",
                    content: "+",
                    title: "Zoom in"
                },
                "out": {
                    cssClass: "zoomButton zoomOut",
                    content: "−", // minus sign
                    title: "Zoom out"
                }
            }
        }
    }
}

Note: at the beginning, I though about adding a complete HTML tooltip like in the map, but title attribute was quite sufficient for this task.

[neveldo]

What if a user add a button "myCustomButton" in the conf ? Maybe we should check for fnZoomButtons[type] existence

[Indigo744]

This is a good idea indeed.
Moreover, should we allow the user to add custom buttons?

[neveldo]

I was wondering it too :) Maybe I'm wrong but I don't think it will be a common need to add custom zoom buttons. Moreover, the user will still can add custom buttons freely, without using mapael conf.

[neveldo]

Thank you for this new feature :) Maybe the UPGRADE.md should be updated regarding the replacement zoomInCssClass and zoomOutCssClass ?

[Indigo744]

Done :)

[neveldo]

Thank you :)