Workarounds for Xamarin.iOS app with EFCore 2.0

## Updated to current known issues and workarounds:

- ~~For Xamarin.Android, use package.config instead of PackageReference (dependent on https://github.com/xamarin/xamarin-android/issues/1196).~~
- For Xamarin.Android, try changing AndroidLinkMode to SdkOnly ( https://github.com/aspnet/EntityFrameworkCore/issues/11027#issuecomment-374425403) or other workarounds to preserve additional reflection metadata, e.g. `[assembly: Preserve (typeof (System.Linq.Queryable), AllMembers = true)]` (dependent on https://github.com/aspnet/EntityFrameworkCore/issues/10963) or using a [LinkDescription.xml]( https://github.com/cwrea/XamarinTodo/blob/master/Todo.Android/LinkDescription.xml) file.
- For SQLite, use `SQLitePCL.Batteries_V2.Init()` (see https://github.com/ericsink/SQLitePCL.raw/wiki/SQLitePCL.Batteries.Init).
- Tooling is blocked on the fact that the linker used by Xamarin removes assembly level attributes (see https://github.com/xamarin/xamarin-macios/issues/3655).

Good sample app link applying workarounds by @cwrea: https://github.com/cwrea/XamarinTodo/tree/master

## Original Issue:
_From @alexdrl on November 21, 2017 8:44_

A Xamarin.iOS app with EFCore 2.0 needs a call to

```c#
SQLitePCL.Batteries_V2.Init();
```

If the call is not made, the app initialization throws this error message.

```
You need to call SQLitePCL.raw.SetProvider(). If you are using a bundle package, this is done by calling SQLitePCL.Batteries.Init().
```
Like explained [here](https://github.com/ericsink/SQLitePCL.raw/wiki/SQLitePCL.Batteries.Init)

### Steps to reproduce
Xamarin.iOS project working with EFCore 2.0. Solution with a common .NET Standard project which shares code between iOS and Android, using PackageReference.

### Further technical details
EF Core version: 2.0.0
Database Provider: Microsoft.EntityFrameworkCore.Sqlite
Operating system: iOS
IDE: Visual Studio 15.4

_Copied from original issue: aspnet/EntityFrameworkCore#10361_