Adds navigation control buttons on top of the canvas layer to allow touch screen users to pan or zoom the chart.

/* Flot plugin that adds some navigation controls on top of the canvas layer to allow users pan or zoom the graph. This is even more helpful for the touch screen users.

Usage:
Inside the <head></head> area of your html page, add the following line:

<script type="text/javascript" src="http://zizhujy.com/Scripts/flot/jquery.flot.navigationControl.js"></script>

Now you are all set, there will be pan and zooming controls appear on your canvas.

Online examples:
http://zizhujy.com/FunctionGrapher is using it.

Dependencies:
These navigation controls would only work if you have referenced jquery.flot.navigation.js plugin and enabled it already.

Customizations:
    options = {
        homeRange: {xmin:-10,xmax:10,ymin:-10,ymax:10},
        panAmount: 100,
        zoomAmount: 1.5,
        position: {left: "20px", top: "20px"}
    };

To make the control symbols (+, -, ←, ↑, →, ↓, ⌂) more beautiful, you may include your own icon fonts css file, the symbols 
have the css class 'icon' for you to hook.