Fix ngdoc generated for scope methods

Create a dummy `lbServices.{model}.{scope}` object that groups all
nested methods except the top-level query.

Before this change, scope methods were mixed with regular model methods,
because ngdoc/docular does not support method names with a dot.
Hide original scope methods from ngdoc

Remove `prototype$__{op}_{scope}__` from ngdoc. These methods don't work
correctly and are included for backwards compatibility only.
Update dependencies

Most notably:
  express to 4.x
  loopback to 2.x