Migrate to AndroidX

• Update Gradle plugin
• Fix nullable annotation in getBinding()

• Update dependencies (support, build tools, gradle)
• Fix issue with viewmodels that use generic types

Critical issue fixed that was introduced two days ago in 1.3.0 - please update to 1.3.1 (issue is related to the new getViewOptional() method).

Added getViewOptional() method which is guaranteed to be non-null. It will return a dummy implemenation in case the View is not null.
Removed the need to override getViewModelClass, the ViewModel class is now automatically extracted from the ViewModel class definition.

Fix proguard settings.

Remove wrong jetbrains annotations import.

• Added default (null) implementation of getViewModelConfig() to the ViewModelBaseActivity so you don't need to implement it for your Activities.

• Added better support for FragmentStatePagerAdapter by adding ViewModelStatePagerAdapter.java.
• Breaking change: Added removeViewModel() to IView. You don't need to make any changes if you are using the default ViewModelBaseFragment. Otherwise you need to implement this method and return null in case you don't need data binding.

• Added support for data binding
• Breaking change: Added getViewModelConfig() to IView. You don't need to make any changes if you are using the default ViewModelBaseFragment. Otherwise you need to implement this method and return null in case you don't need data binding.