afbb9c2717
Enable Mapbox Metrics by default when Settings.bundle is absent, but allow Settings.bundle to override the default. Don’t register defaults for non-Mapbox preferences. The two-phase registration ensures that the defaults don’t default to unexpected values, yet gives the developer a chance to call `+[MGLAccountManager mapboxMetricsEnabledSettingShownInApp]` before the hard assertion. Fixes #1518.