interpret table names in context of mountPath and basePath (Fixes #198)

It's not clear if `out` can be a path or just a file name, and it's not clear if it should be an absolute path or a relative path (or both), and also what the interpretation of that absolute / relative path is given the base path.

Probably, if the `out` is relative, it should be interpreted with respect to `[path]`, while if it's absolute, it should retain it's absolute positioning semantic. This is consistent with how paths appear in the query itself.

In any case, path returned by this method should probably be absolute to avoid any confusion.