Client side export / offline exporting

[golimarrrr]

Exporting charts requires an internet connection which is not always available, and also with HTML5 the PNG/JPEG rendering can be done in the browser. It can be achieved like this:

http://www.highcharts.com/docs/export-module/client-side-export

I have it working on my system by:

• adding "offline-exporting.js" to the script list in HighChart.java and compiling
• adding the offline-exporting.js file to the highchartsapi folder (https://github.com/downdrown/VaadinHighChartsAPI/tree/master/src/main/resources/at/downdrown/vaadinaddons/highchartsapi)
• and also replacing the other JavaScript files in that folder with the current ones at highcharts.com, as the old ones there seemed to be incompatible with the current offline-exporting.js file.
• cleaning browser cache and Eclipse project as it was still taking the old .js from somewhere

Is it possible to merge this into the project? (along with an option to choose online/offline export)