Update sw.opentsdbwidget.js

[cdesbouche-acipia]

Add option "download as image" for each graph

[boxcla]

Hi @cdesbouche-acipia, thanks for the pull request. Before we can merge it, we need you to sign our Contributor License Agreement. You can do so electronically here: http://opensource.box.com/cla

Once you have signed, just add a comment to this pull request saying, "CLA signed". Thanks!

[cdesbouche-acipia]

CLA signed

[boxcla]

Verified that @cdesbouche-acipia has just signed the CLA. Thanks, and we look forward to your contribution.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}