Add minimal space management (get/create/delete).

Hi,
This PR is a minimal API to manage space.
Create and delete are restricted to current organization retrieved by current space.
Space creation only support required parameters (no user support, security-groups, etc...).
Get is not restricted to current org.

This could be part of story Add APIs for managing spaces [https://www.pivotaltracker.com/story/show/53169449]

I'll try to add user support in space management. Do you have some design preferences (like adding this support in space creation, or add a new command, or ....) ?
Regards,
 Olivier