Restructure pkg/unittest and pkg/webdriver to follow the pub conventions.

pkg/unittest/lib/operator_matchers.dart

 // Copyright (c) 2012, 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.
 
-part of unittest;
+part of matcher;
 
 /**
  * This returns a matcher that inverts [matcher] to its logical negation.
  */
 Matcher isNot(matcher) => new _IsNot(wrapMatcher(matcher));
 
 class _IsNot extends BaseMatcher {
   final Matcher _matcher;
 
   const _IsNot(Matcher this._matcher);
@@ skipping 156 matching lines @@
          return true;
        }
      }
      return false;
   }
 
   Description describe(Description description) =>
     description.addAll('(', ' or ', ')', _matchers);
 }