Adding Login Scanner for MyBook Live

This is a LoginScanner auxiliary module for Western
Digital MyBook Live NAS devices as well as the spec
for testing.
I think I mentioned this before, but why are you setting the method and URI defaults here and then not using the currently set values in attempt_login?  IOW, in the event that a user needs to run this module with a different method or against a different URI (unlikely, but not impossible), they can't do that.