switch UploadResults to use getters, hide internal data, for all but .uri

switch UploadResults to use getters, hide internal data, for all but .uri

This hides attributes with e.g. _sharemap, and creates getters like
get_sharemap() to access them, for every field except .uri . This will
make it easier to modify the internal representation of .sharemap
without requiring callers to adjust quite yet.

".uri" has so many users that it seemed better to update it in a
subsequent patch.