Write feature detection for image data clipboard paste.

Ideally we can avoid browser detection, and instead opt for feature detection instead. See https://github.com/Modernizr/Modernizr/pull/659 for a discussion of approaches. It may be that we need to do browser detection.

Testing notes

• In IE8, IE9, IE10, the Java applet should be used, if it's installed, otherwise it should show "unsupported".
• In all other browsers (IE11, latest FF, Chrome, Safari), the HTML5 version should be used.
• Check IE10 in Windows 8 VM from http://modern.ie — gtanczyk had problems in the past.
• Ensure QUnit tests pass.