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}
Merge branch 'devel' into api-headnode-put-delete

Conflicts:
	haas/cli.py
	haas/server.py
	tests/unit/api.py
Fix CLI help messages for headnode_{create,delete}
Merge branch 'devel' into api-headnode-put-delete

Conflicts:
	haas/cli.py
	haas/server.py
Merge pull request #134 from gsilvis/api-headnode-put-delete

Api headnode put delete