Use deviceconsole instead of idevicesyslog to capture iOS real device logs

idevicesyslog often misses parts of the log, or stops capturing the log until the end of the test. [deviceconsole](https://github.com/rpetrich/deviceconsole) works in the same way, but much better.

Resolves #3202 and #2855.

One further issue: The server flag is `--show-sim-log` though as far as I can tell it is how you turn on the real device logs as well. At least, it turns them on.
We use `ideviceinstaller` in [ios.js](https://github.com/appium/appium/blob/master/lib/devices/ios/ios.js#L823).