Implement WebSettings::getTextZoom() and WebSettings::setTextZoom()

add https://developer.android.com/reference/android/webkit/WebSettings.html#setTextZoom(int) and https://developer.android.com/reference/android/webkit/WebSettings.html#getTextZoom() implementations from API level 14

with a test but sadly not sure how to run it

$ mvn test

doesn't run TestWebSettingsTest file ...