We want to serialize these label values into the secondary index so we
can avoid database lookups and submit rule evaluation when rendering
change tables. The easiest way to do this is to use Gerrit's protobuf
support to convert them to protos to store in the index. This is built
around @Column annotations, so use that.
Move to the reviewdb package to pick up the necessary gwtorm
dependency.
Change-Id: I02b4a14404a8d8d72452fea68f0c25f3cbb377f8
50a7a3a61d