Chrome 49 does not load the HTML5 client

[ffdixon]

When testing BigBlueButton in older version of Chrome, the client fails to load (shows only a blue screen).

There is an exception thrown in the console

Need to add detection for versions of Chrome (at least 49 or earlier) and warn the user that they need to use a more recent version.

Reported here in bigbluebutton-users

https://groups.google.com/d/msg/bigbluebutton-users/DHK_h7CuAek/G4C5-wvVCgAJ

[capilkey]

This was addressed in #7303. People on older browsers will be served an alternate minimal application that will tell them to update their browsers.