Move back to using Chrome on OSX closes #2043

This moves back to using Chrome on OSX but making it obvious that it's Chrome to avoid any user issues with running Chrome itself. This also includes a more general refactoring of the browser launching code, as it had gotten a little convoluted after various revisions. This should be a bit more maintainable and portable.
Oh, I see, we run it as an app on Linux.  To make this distinction clearer, I might make app a boolean flag on addDefaultChromeArgs, at which point your comment here makes more sense.

Also, rather than having it be addDefaultChromeArgs, I might make it buildChromeCommand and have it take care of finding the chrome executable from amongst all possible paths.