Extract User from Actors context

Mobilizon.Actors.User -> Mobilizon.Users.User
Also Mobilizon.Actors.Service now become Mobilizon.User.Service
And Mobilizon.Users and Mobilizon.UsersTest is introduced.

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/mobilizon/actors/bot.ex

@@ -4,7 +4,8 @@ defmodule Mobilizon.Actors.Bot do
   """
   use Ecto.Schema
   import Ecto.Changeset
-  alias Mobilizon.Actors.{Actor, User}
+  alias Mobilizon.Actors.Actor
+  alias Mobilizon.Users.User
 
   schema "bots" do
     field(:source, :string)