add container manager test

PluginsRegister 不再对外暴露，需要手动注册插件请使用  FlutterBoost.instance().engineProvider().getPlugins().add(new FlutterPlugin());

- add ContainerManagerState test group
- containerCounts should change based on the number of pages

add analysis_options.yaml and fix error

- test `of` method, try to get the ContainerManagerState in the ancestor node
- test `tryOf` method, try to get the ContainerManagerState in the ancestor node

[sync] 2020/3/2

支持Hero动画

如何设置页面横屏

# Conflicts:
#	android/build.gradle
#	android/src/main/java/com/idlefish/flutterboost/Platform.java

- test `of` method, try to get the ContainerManagerState in the ancestor node
- test `tryOf` method, try to get the ContainerManagerState in the ancestor node

[sync] 2020/2/21

remove useless code in boost_page_route

-  boost_page_route_test.dart
test `of` and `tryOf` method

- Remove overridden buildTransitions method because it seems useless.

- Also removed Stub, didn't find it used.