(Major) Migrate GD API URLs

GoodData has been migrating to Rackspace since the beginning of February, and they are changing their domains in the process.
The old domains remain available "for a limited period of time necessary for the smooth transition".

Fixes dataset upload error on new machine: http://stackoverflow.com/questions/21655709/etl-pull-failing-error-message-giving-mixed-messages

Details at http://developer.gooddata.com/article/rackspace-project-migration-process