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 gotcha. Yeah for whatever reason LanternUtils.class.getResourceAsStream wasn't working when I first implemented that method for extracting flashlight, but again I find those two calls and their relationship to classloaders endlessly confusing.