Add sensible default values in python client
Add sensible default values in python client

* Use 0 for content-length if no header is passed for download
* Use empty string for name if none is set. Helps during mocked interaction.

sutartmelson/girder,Kitware/girder,sutartmelson/girder,girder/girder,girder/girder,girder/girder,jbeezley/girder,jbeezley/girder,RafaelPalomar/girder,sutartmelson/girder,Xarthisius/girder,adsorensen/girder,manthey/girder,Kitware/girder,data-exp-lab/girder,kotfic/girder,jbeezley/girder,sutartmelson/girder,manthey/girder,adsorensen/girder,adsorensen/girder,girder/girder,kotfic/girder,manthey/girder,data-exp-lab/girder,data-exp-lab/girder,kotfic/girder,RafaelPalomar/girder,Xarthisius/girder,adsorensen/girder,RafaelPalomar/girder,data-exp-lab/girder,Xarthisius/girder,sutartmelson/girder,data-exp-lab/girder,Xarthisius/girder,Xarthisius/girder,Kitware/girder,jbeezley/girder,manthey/girder,Kitware/girder,adsorensen/girder,RafaelPalomar/girder,kotfic/girder,kotfic/girder,RafaelPalomar/girder