This change allows the user to specify the format of the log file to be
generated by the `WPT.sh` script. Multiple logging arguments may now be
specified.
The supported logging arguments are: `--log-raw`, `--log-unittest`,
`--log-xunit`, `--log-html`, `--log-mach`, `--log-tbpl`,
`--log-grouped`, `--log-chromium`, `--log-wptreport` and
`--log-wptscreenshot`. These arguments act the same as the equivalent
arguments supported by `wpt run`.
The short `--log` argument may also be used as an alias for `--log-raw`.
The Web Platform Tests runner requires that some hostnames point to
localhost when running the tests locally. We now append these hostnames
to `/etc/hosts` if they aren't already present.
