Restructure the public API for server

pkg/analysis_server/lib/plugin/index/index_core.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library analysis_server.analysis.index.index_core;
+library analysis_server.plugin.index.index_core;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 /**
  * Return the integer value that corresponds to the given [string]. The value of
@@ skipping 255 matching lines @@
  */
 abstract class Relationship {
   /**
    * Return a relationship that has the given [identifier]. If the relationship
    * has already been created, then it will be returned, otherwise a new
    * relationship will be created
    */
   factory Relationship(String identifier) =>
       RelationshipImpl.getRelationship(identifier);
 }