Added support for included groups

This change adds a new item to the group configuration: a list of
groups whose members should be included in this one.  This makes it
possible to set up a hierarchy of included groups, which can make it
easier to maintain complex access control lists.

To accomplish this, two new database tables were added,
called AccountGroupIncludes and AccountGroupIncludesAudit.
The relevant support code was added around them, largely based on
the existing code for handling indivdual account membership.  In
addition, caches for group information were added, paralleling the
caches that already exist for accounts.

Change-Id: Ib6990c17739f28f38bc13961143db7ce79251567

gerrit-server/src/main/java/com/google/gerrit/server/account/GroupIncludeCache.java

@@ -0,0 +1,27 @@
+// Copyright (C) 2011 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.account;
+
+import com.google.gerrit.reviewdb.AccountGroup;
+
+import java.util.Collection;
+
+/** Tracks group inclusions in memory for efficient access. */
+public interface GroupIncludeCache {
+  public Collection<AccountGroup.Id> getByInclude(AccountGroup.Id groupId);
+
+  public void evictInclude(AccountGroup.Id groupId);
+}
+