设置navigationbar 颜色，主题

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[[UINavigationBar appearance] setBarTintColor:COLOR_RGB(0, 159, 239)];
[[UINavigationBar appearance] setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor whiteColor]}];
[[UINavigationBar appearance] setBackIndicatorImage:[UIImage imageNamed:@"btn-back"]];
[[UINavigationBar appearance] setBackIndicatorTransitionMaskImage:[UIImage imageNamed:@"btn-back"]];
[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -100) forBarMetrics:UIBarMetricsDefault];