fix(ios): set dark statusbar style if defined in plist

[MarkChrisLevy]

When dark status bar style was defined in plist it wasn't remembered in statusBarStyle and as a result preferredStatusBarStyle always returned .default, which caused flicker of the status bar . Partially closes #1761 (in terms of ios issues).

[jcesarmobile]

Even with the if available, that will fail to compile on Xcode 10, which is still supported. You can use the raw value instead, I think I used it in Statusbar.swift, take a look.
Also, there are other possible values other than default, light and dark that behave as light , so the second if should be statusBarStyle != "UIStatusBarStyleDefault"
The linked issue is an android issue.

[MarkChrisLevy]

@jcesarmobile ok, I will make appropriate changes. I was focused mainly on latest xcode and ios, totaly forgot about older sdk ;-) And yes, #1761 was about android, but there was a comment #1761 (comment), that was reporting similar issue on ios, so that is why I mentioned about it.

[MarkChrisLevy]

@jcesarmobile Done :-)

[MarkChrisLevy]

@jcesarmobile Is it ok now?

[jcesarmobile]

Fixed the code indentation as we use 2 spaces instead of 4, and added a TODO to remember to change the rawValue once Xcode 10 support is dropped.

Other than that looks good, will merge once tests finish. Thanks!