Support multi-select in storage UI.

When caller has specified that multiple documents are okay, enable
multi-select action mode.  Currently only allows document selection,
not directories.  Returns multiple documents through ClipData.

Fix bug where GridView was stuck with 2 columns on tablets.

Change-Id: Id49b29a86330639b56fa116d37e7f0d874980c5b
diff --git a/res/values/dimens.xml b/res/values/dimens.xml
new file mode 100644
index 0000000..e5c4138
--- /dev/null
+++ b/res/values/dimens.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2013 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.
+-->
+
+<resources>
+    <dimen name="grid_width">180dp</dimen>
+</resources>