Refactor bottomTabs options applying mechanism. Both bottomTab and bottomTabs presenters were part of the base UIViewController class which was wrong. This commits moves them to the BottomTabsController.

This refactor mostly contains the following

* Detach bottomTabPresenter from basePresenter
* Create tabBarItem appearance on presenter init
* Refactor bottomTabPresenter
* Refactor bottomTabPresenter
* Move appearance creation to bottomTabsController
* Merge child options with direct child controller

This commit adds initial support for passing null as a valid value for color properties.
When a color property is applied, if it wasn't specified then the default color is applied. Now, when null is passed, no color will be applied
leaving the last color applied as is.

This is useful when showing an Overlay and you'd like to keep the current StatusBar color unaffected. Another usecase would be when you'd like to avoid coloring an icon in BottomTabs.

Add support for dot indicator to BottomTabs.