Echarts panel for grafana

1. $ npm install
2. $ grunt
3. Restart Grafana-server.
4. Add a echarts panel.
5. Add your echarts option to EchartsOption in edit page.

1. Support liquidfill and wordcloud plugin.
2. You can import other map ,just copy it to libs folder and import it in echarts_ctrl.js.
3. dark.js is the theme file ,If you want to customize theme.
4. Response belongs to your url has been saved as echartsData.
5. Calling the timer function as the callback of callInterval(callBack, interval) function prevents it from being repeatedly triggered.