Cleanup minor issues in rest_api.md

- Spacing is now more consistent
- A few calls were slightly rearranged
Make the 'group' parameter explicit

I think this way is clearer, and it's actually shorter too.
Change 'label' to 'id' in rest_api.md
Add missing API calls to rest_api.md

Some of them don't have an obvious REST interface---those are marked at the
end.
Miscellaneous fixes to apidesc.md

These are similar to the changes made to rest_api.md.
Fix small typos in node_{register,delete}_nic
Fix bad prototype for headnode_{create,delete}

In the API documentation, these functions take a headnode name and a /group/
name---but in api.py, they took a headnode name and a /project/ name.  This
doesn't make sense, because we also have the API call
'project_connect_headnode'.  This commit fixes both the function and its
corresponding unit test.
Add REST API function for headnode_{create,delete}
Add CLI functions for headnode_{create,delete}
Merge branch 'api-group-ownership-consistency' into api-headnode-put-delete

Conflicts:
	haas/api.py
Add tests for failure cases of headnode_{put,delete}
Add unit tests for network_{create,delete}

These tests currently ALL fail, because the functions in api.py are wrong.
Add more failure-mode tests for project-detach/attach-node
Add REST wrappers for project_{connect,detach}_node
Add CLI wrappers for project_{connect,detach}_node
Replace Vlan with Network in model.py

Also do trivial fixes to api.py to make this work.

Currently, Network takes a parameter 'nic_id'.  I don't know what this does,
and the API doesn't have a place to specify it.  So, I've set it as 'FIXME'.
This should be fixed.

All tests now pass.
Add REST wrapper for network_{create,delete}
Add CLI wrappers for network_{create,delete}
Remove 'nic_label' column from Network table
group_create/delete sprint implementations