Bot nameplates (#7391)

* Store actor type in database

* Add bot nameplate to web UI, add setting to preferences, API, AP
Fix #7365

* Fix code style issues

db/migrate/20180506221944_add_actor_type_to_accounts.rb

@@ -0,0 +1,5 @@
+class AddActorTypeToAccounts < ActiveRecord::Migration[5.2]
+  def change
+    add_column :accounts, :actor_type, :string
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2018_04_16_210259) do
+ActiveRecord::Schema.define(version: 2018_05_06_221944) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -75,6 +75,7 @@ ActiveRecord::Schema.define(version: 2018_04_16_210259) do
     t.bigint "moved_to_account_id"
     t.string "featured_collection_url"
     t.jsonb "fields"
+    t.string "actor_type"
     t.index "(((setweight(to_tsvector('simple'::regconfig, (display_name)::text), 'A'::\"char\") || setweight(to_tsvector('simple'::regconfig, (username)::text), 'B'::\"char\")) || setweight(to_tsvector('simple'::regconfig, (COALESCE(domain, ''::character varying))::text), 'C'::\"char\")))", name: "search_index", using: :gin
     t.index "lower((username)::text), lower((domain)::text)", name: "index_accounts_on_username_and_domain_lower"
     t.index ["uri"], name: "index_accounts_on_uri"