loader: make some entities public and improve doc

Signed-off-by: Jean Privat <jean@pryen.org>
loader: add a public itentified_files attribute

Signed-off-by: Jean Privat <jean@pryen.org>
nitls: stop intruding loader

Signed-off-by: Jean Privat <jean@pryen.org>
contrib/online_ide: intrude loader instead of modelbuilder

Signed-off-by: Jean Privat <jean@pryen.org>