Improve OpenAPI space integration

[tulir]

Parts:

• Publish button (parent to Add Space publish button #322, PR Add publish button #362)
• Non-modular upload system (parent to Remove upload system modularity #325, PR Remove upload system modularity #332)
• Version handling (parent to Add API spec version browser with Space as the backend #323)
• Choosing from a list of APIs
• Configurable server (parent to Allow easily changing which OpenAPI space server to use #346)
• Registering (parent to Add way to register to space #304, PR Add registering to Space #351 )
• Indicate logged in status (parent to Indicate user login status and allow logout #309)
• More?