Allow to tag reviews

In order to be able to filter out non-human comments and votes we need
to tag them.

This change introduces new property to the ReviewInput object called
'tag'. This allows us to add some meta information about where this vote
come from. Then in the UI we can show/hide comments and votes that have
different tags.

Also ApprovalInfo, CommentInfo and ChangeMessageInfo were extended to
include value of 'tag' property read from DB.

To be able to persist those data new column (tag) was introduced to
change_messages, patch_set_comments and patch_set_approvals tables.

Change-Id: If6378c5a9f4e0673c00ab348297549f27a06110b
Signed-off-by: Dariusz Luksza <dariusz@luksza.org>

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/ReviewInput.java

@@ -26,6 +26,8 @@ public class ReviewInput {
   @DefaultInput
   public String message;
 
+  public String tag;
+
   public Map<String, Short> labels;
   public Map<String, List<CommentInput>> comments;
 

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/ApprovalInfo.java

@@ -17,6 +17,7 @@ package com.google.gerrit.extensions.common;
 import java.sql.Timestamp;
 
 public class ApprovalInfo extends AccountInfo {
+  public String tag;
   public Integer value;
   public Timestamp date;
 

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/ChangeMessageInfo.java

@@ -18,6 +18,7 @@ import java.sql.Timestamp;
 
 public class ChangeMessageInfo {
   public String id;
+  public String tag;
   public AccountInfo author;
   public Timestamp date;
   public String message;

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/CommentInfo.java

@@ -18,4 +18,5 @@ import com.google.gerrit.extensions.client.Comment;
 
 public class CommentInfo extends Comment {
   public AccountInfo author;
+  public String tag;
 }