Added a cli command for user_delete

Did some light interactive testing, but need to figure out how to write
unit tests for the cli.
Added cli/server components of node_register
Added a test for duplicate node_register calls.

These should throw an error, and they do.
Added group_{add,remove}_user to haas.server and haas.cli.

Conspicuously, there's no group_create yet, so testing this manually is
a bit awkward, but can be done. It's on the TODO list.

Additionally, the functions had been omitted from the docs, so they've
been added there as well.
haas cli now prints out argument names as part of the help.

You now get output like:

    ...
    user_create <username> <password> # comment
    ...

instead of:

    ...
    user_create # comment
    ...

The arguments are pulled from the functions themselves.
The cli was using the wrong url for project_deploy, fixed.
Merge pull request #127 from gsilvis/api-group-ownership-consistency

Api group ownership consistency
Merge pull request #118 from zenhack/user_delete

Added a cli command for user_delete
Merge pull request #128 from zenhack/node_register

Node register
Merge pull request #129 from zenhack/project_deploy/cli-fix

The cli was using the wrong url for project_deploy, fixed.
Merge remote-tracking branch 'moc/devel' into group_add/remove_user

Conflicts:
	haas/cli.py
	haas/server.py
Merge pull request #131 from zenhack/group_add/remove_user

Group add/remove user
Tweak model for Hnic

- The headnode field is now non-nullable
- The constructor now takes a 'group' argument
Add API calls headnode_{create,delete}_hnic
Add unit tests for headnode_{create,delete}_hnic
Add REST wrappers for headnode_{create,delete}_hnic
Add CLI wrappers for headnode_{create,delete}_hnic
Merge remote-tracking branch 'moc/devel' into cli-argnames

Conflicts:
	haas/cli.py

In addition to fixing the conflicts, I updated some of the docstrings
for the new functions to better mesh with the help output.
Merge pull request #130 from zenhack/cli-argnames

haas cli now prints out argument names as part of the help.
Merge pull request #136 from gsilvis/api-headnode-create-delete-hnic

Api headnode create delete hnic