Merge: Cleanup loader

Because #1250 is starting to stall and that my rewrite of the loader is not going well, I started last night an alternative approach: improve the existing loader in small steps.

This PR contains small cleaning on the loader, mainly documentation, small refactorization and bugfixes.
This is a small part of bigger modification still in progress, but I expect these commits to be good enough to be merged.

Pull-Request: #1638
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>