Clean up imports in analysis_server and analyzer_cli (and one missed in analyzer)

pkg/analysis_server/lib/src/computer/computer_hover.dart

 // Copyright (c) 2014, 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 computer.hover;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart'
     show HoverInformation;
+import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/ast.dart';
-import 'package:analyzer/src/generated/element.dart';
 
 /**
  * Converts [str] from a Dart Doc string with slashes and stars to a plain text
  * representation of the comment.
  */
 String _removeDartDocDelimiters(String str) {
   if (str == null) {
     return null;
   }
   // remove /** */
@@ skipping 110 matching lines @@
   String _computeDocumentation(Element element) {
     if (element is ParameterElement) {
       element = element.enclosingElement;
     }
     String dartDoc = element.computeDocumentationComment();
     return _removeDartDocDelimiters(dartDoc);
   }
 
   static _safeToString(obj) => obj != null ? obj.toString() : null;
 }