Merge branch 'admin-config' into 'develop'

Admin config

See merge request pleroma/pleroma!1328

priv/repo/migrations/20190622151019_add_group_key_to_config.exs

@@ -0,0 +1,12 @@
+defmodule Pleroma.Repo.Migrations.AddGroupKeyToConfig do
+  use Ecto.Migration
+
+  def change do
+    alter table("config") do
+      add(:group, :string)
+    end
+
+    drop(unique_index("config", :key))
+    create(unique_index("config", [:group, :key]))
+  end
+end