add appStatusYml to the codegen to allow users to separate the error codes

[stevehu]

1. This will suppress the warning message during the startup.
2. It will encourage users to use the secondary status file to define the error codes for the application. This file will merge with the framework status.yml during the server startup.
3. generate values.yml to encourage usage

[stevehu]

add appStatusYml to the codegen to allow users to separate the error codes light-codegen master