Load(): Make it able to load members stored in various formats
Currently the only supported member file name is a path with the member number ranging from 0 to nmemb - 1. But in some cases it ranges from 1 to nmemb or contains more padding 0s (0001, 0002, ...) or is in the format rNiMpO, where N, M and O can vary. A solution has to be thought and coded.