Convert some value classes to AutoValue

These classes were found by searching for custom hashCode
implementations, and omitting some cases:

 - Classes requiring custom serialization, which is not supported[1][2].
 - Most instances with custom hashCode or equals implementations,
   where the code savings is not as significant.
 - All classes in the extension API. We may migrate these eventually,
   but let's avoid this large backwards incompatible change until
   we're more used to AutoValue elsewhere.
 - All classes in the UI package.[3]

There are likely still more value classes that were missed by this
search that do not implement equals or hashCode.

[1] https://github.com/google/auto/tree/master/value#serialization
[2] This excludes, among other things, all persistent cache keys. It
might be possible to convert persistent caches to use a key
marshalling strategy other than Java serialization, but probably not
without invalidating all existing entries.
[3] This should still be possible as generated classes are generally
GWT compatible.

Change-Id: I96796b9879b7e487b80949b63115ac4032180f8b
diff --git a/gerrit-httpd/BUCK b/gerrit-httpd/BUCK
index 97d28f0..a4d127d 100644
--- a/gerrit-httpd/BUCK
+++ b/gerrit-httpd/BUCK
@@ -26,6 +26,7 @@
     '//lib:gwtorm',
     '//lib:jsch',
     '//lib:mime-util',
+    '//lib/auto:auto-value',
     '//lib/commons:codec',
     '//lib/guice:guice',
     '//lib/guice:guice-assistedinject',