Added custom navigationBarClass support to NavigationController

[phlippieb]

#1074

Adds an initializer to NavigationController that takes a custom navigation bar class parameter; this parameter is simply passed to super.

This extends NavigationController with the ability to be initialized with a user-defined subclass of NavigationBar.

[phlippieb]

Two other ways I can think of doing this are:

1. Make the new init a designated initializer, and make the old init (that always passes NavigationBar.self to super) a convenience init.
2. Give the navigationbarClass parameter a default value of NavigationBar.self

If you prefer either of those, I'll update my PR.

[OrkhanAlikhanov]

Hey @phlippieb , thank you for your contribution. I would go with your first option. Which I guess what you meant should look like this, but with 2-spaced indention just like other parts of the file:

public override convenience init(rootViewController: UIViewController) {
  self.init(rootViewController: rootViewController, navigationBarClass: NavigationBar.self)
}
  
public init(rootViewController: UIViewController, navigationBarClass: AnyClass?) {
  super.init(navigationBarClass: navigationBarClass, toolbarClass: nil)
  setViewControllers([rootViewController], animated: false)
}

If @DanielDahan approves either option, You may remove the commit rebase development branch again and reapply changes and do one clean commit. To be honest, I am not sure about the second option.

[daniel-jonathan]

Thank you!