Add DatePickerDialog to layoutlib [DO NOT MERGE]

Includes android.app.DatePickerDialog in the layoutlib.jar

Bug: http://b.android.com/28318
Change-Id: I583dde4a8b88204bf98bfca8d91470e1aa4719ce
(cherry picked from commit c2016d4073)

tools/layoutlib/create/src/com/android/tools/layoutlib/create/Main.java

@@ -114,6 +114,7 @@ public class Main {
                         "android.os.*",  // for android.os.Handler
                         "android.database.ContentObserver", // for Digital clock
                         "com.android.i18n.phonenumbers.*",  // for TextView with autolink attribute
+                        "android.app.DatePickerDialog",     // b.android.com/28318
                     },
                     excludeClasses,
                     new String[] {