Improvement: SmugMug limits

[pbtrung]

SM has a limit of "5000" on everything: 5000 subfolders per folder, 5000 galleries per folder, 5000 pictures per gallery, etc. Furthermore, it can only contain folder trees that go five folders deep (SmugMug API). It seems smugcli does not check those limits before uploading, which results in errors or ignoring folders/pictures.
The SM web uploader does check those limits: it does not allow uploading if one of those limits is violated.