allow more convenient recursive key for afd:msg
source refactoring
change default message formatter to JDKMessageFormatFormatter
use key as default message for recursive keys
source refactoring for i18n message helper mechanism
remove support for dynamic snippet and embeding because it is not necessary
remove unnecessary reverse injection related logic
save trace info to context for current rendering template file and executing snippet
save current executing request handler trace info to context
allow retrieve message bundler via corresponding template file or request handler
remove unnecessary sample source