Migrate some settings to Settings class and constants
Partial fix for GRAILS-11101 "Remove dependency on commons-fileupload and use Spring's StandardServletMultipartResolver". Only works when run Spring Boot. Need to improve 'grails-web-initializer' to configure MultipartConfigElement
Package renaming 'org.codehaus' to 'org.grails'
Move some classes to public API for 'grails-async'