display troubleshooting info in About dialog

[pixelzoom]

Display anything that would be useful for identifying the browser and host platform. On mobile devices especially, it's very inconvenient to find browser version, OS version, etc. and we're going to need that info to troubleshoot. If it's in the About dialog, the process of getting info will be the same on all platforms - we can ask users to open the About dialog and send us a screenshot.

[pixelzoom]

8/1/13: @ariel-phet requested that this be done as soon as possible, to facilitate testing and bug reporting.

[samreid]

Put it in the about dialog, make the text selectable. Assigning to @jonathanolson since he said some scenery tweaks would be necessary to make copy/paste available.