Move all custom fields and form layout customisations into the database (cached by redis)

The reason for this is that in enterprise environments, we want to be able to run containers and deployment pipelines using a tool such AWS CodePipeline (and many others). At the moment, customisations via the studio rely on many files that are stored in the custom folder - if the definition of custom fields and forms could be moved to the database (and cached in redis for performance), we could realistically run SugarCRM in docker serverless environments. At the moment, if we want to allow this, we need to export the changes in the studio on each change, or have shared storage such as an NFS, which significantly degrades the performance of the system. The above simple change would enable us to have true devops without sacrificing customisability.