BURs: fix tags field not finding all BURs with that tag.

Fix the Tags field in the BUR search form not finding all BURs
mentioning that tag. Specifically, tags that were part of a mass update,
and that were prefixed with `~` or `-` (OR tags and NOT tags), weren't
indexed as tags affected by the BUR.

This requires re-running script/fixes/064_initialize_bulk_update_request_tags.rb
to fix old BURs.

script/fixes/064_initialize_bulk_update_request_tags.rb

@@ -1,11 +1,14 @@
 #!/usr/bin/env ruby
 
-require_relative "../../config/environment"
+require_relative "base"
 
-BulkUpdateRequest.transaction do
+with_confirmation do
   BulkUpdateRequest.find_each do |request|
     request.tags = request.processor.affected_tags
-    request.save!(validate: false)
-    puts "bur id=#{request.id} tags=#{request.tags}"
+
+    if request.changed?
+      request.save!(validate: false)
+      puts "bur id=#{request.id} added_tags=#{request.tags - request.tags_before_last_save} removed_tags=#{request.tags_before_last_save - request.tags}"
+    end
   end
 end