Various improvements (hopefully)

This is a small PR with:

- API upgrade
- caching of Id's so you don't need to remember what you're working on. eg. view a data-center, then when you create a server it remembers which data-center you're in. Of course you can override it, meaning the new data-center provided now becomes the current (default) one.
- retrying in the case of provisioning - automatically when needed