Align project files with CodeHarbor

Since both projects are developed together and by the same team, we also want to have the same code structure and utility methods available in both projects. Therefore, this commit changes many files, but without a functional change.

config/database.yml.example

@@ -13,6 +13,9 @@ production:
   <<: *default
   database: codeocean_production
 
+# Warning: The database defined as "test" will be erased and
+# re-generated from your development database when you run "rake".
+# Do not set this db to the same as development or production.
 test:
   <<: *default
   database: codeocean_test