closes #2143

No major changes, just tweaked values a little bit.

* Fab animation duration changed to 120 (previously 200)
* Fab show animation: Scales from 0.6 to 1 (previously 0)
* Fab hide animation: Scales from 1 to 0.6 (previously 0)
* Removed alpha delay from screen animation
* TranslationY value changed from 8% to 5%

* Support showing modals with the default screen push/pop animation

* Set navigation bar color before modal is displayed

* Implement screenAnimationType property

controls animation type of all screens including modals.

added some elaborations to make it easier for developers with no ios experience.

* V2 overlay skeleton (#2097)

* skeleton

* basic test

* remove useless files

* remove useles files

* semicolon

* refactoring

* rm useless files

Since status bar style was applied when the screen was created, this caused a noticeable
artifact in status bar color.

When toggleTabs was called, the visibility state of the BottomTabs
was not persisted. There for, when pushing a screen and popping
the BottomTabs visibility state was set to the value of bottomTabsHidden
from navigatorStyle.

This commit continues the work done in #2057.
When hardware back button is pressed, we handle it accordingly:

1. If screen was pushed with `overrideBackPress: true`, we emit `backPress` event
2. Let `BackHandler` handle the event
3. If the event wasn't handled by `BackHandler`, pop the stack
4. let the system handle the event

This reverts commit 3dd185ecad.

* animation fix

* fix tests

* hide toolbar

* default values

* default values

* tmp commit

* tests

* animated hide

* animated hode improve

* fix topbar

* readme

* lifecycle WIP

* lifecycle alert delay hack

* test fixes

* move topbar to container

* fix tests

* refactor

* refactor WIP

* refactor fix tests

* nav options fallback to parse

* WIP

* topbar background fix

Perform all stack related commands in performOnStack which
doesn't crash when requested stack is no found

* Add a button to the modal example to hide modal

* Render button only for iOS

Until now, buttons would use the same font family used by the title,
this commit introduces navBarButtonFontFamily property which allows to set
a different font family for title and buttons.

fixes #2038

* Support subtitle FontFamily on size on Android

Font family can be either a .ttf/.otf asset or one of the default font families:

* sans-serif (regular)
* sans-serif-light
* sans-serif-condensed
* sans-serif-thin
* sans-serif-medium

* update docs

While working I got a situation in which I wanted to open the side drawer on a button click. But I was not able to that. So I made some changes and now I am able to achieve the required functionality.

This prevented custom react views in navBar from being displayed if AppStyle was used.

* Fix style

* Fix resolving logic

* Fix styling

The only argument to `popTo` is the containerId to pop to, not the current containerId as well.  Also showing `this.props.previousContainerIds` lead me to believe that was included automatically (similar to `this.props.containerId`) so I changed that to avoid confusion.

The new path is `.../lib/ios` not just `/ios`