Document consistency model
Fix several issues in docs/consistency-model.md

- Clarify that some operations don't care about the dirty bit

- Use 'apply' rather than 'deploy'

- Clarify failure mode and idempotency of 'project_apply'

- Fix description of 'node_{attach,detach}_network'

- Document limitation of 'headnode_delete'

- Needlessly reindent paragraph for 'headnode_power_{on,off}'
Use 'frozen' terminology
Rename headnode_power_{on,off} to headnode_{start,stop}
Remove confusing clause in consistency model doc
Put deploy->apply in test suite
Clean up haas/api.py, and write helper for namespaced-searching

This is a terrible commit.  I'm sorry.

- Make the names of arguments to functions be uniform.  Note that I'm
  type-punning the arguments.  They start as strings and turn into objects.
  This should have been a separate commit, but it wasn't when I did it, and I
  found it nearly impossible to separate out.

- Create 'owner' field of namespaced objects.  This replaces the old 'node'
  field on nics, 'headnode' field on hnics, and 'switch' field on ports.  This
  makes the searching much nicer.  (Also fix the small number of tests that
  referenced those fields directly.)

- Write helper functions _must_find_n and _assert_absent_n, for namespaced
  searching, and use them everywhere appropriate
Replace 'connect' with 'attach'
Update docstrings in haas/api.py
Factor out common SQL query
Merge pull request #190 from gsilvis/abstract-get

Namespaced searching
Fixed formatting bug in the dell driver, bad int in printf.
Merge pull request #193 from ryabouza/formatFix

Fixed formatting bug in the dell driver, bad int in printf.
Merge pull request #175 from gsilvis/model-doc

Document consistency model
Update overview.md

Added headnode host as a component of a HaaS installation
Check that HNIC is attached before attaching to bridge

Previously, the code would attempt to attach the HNIC to a network, and hit a
null dereference if it wasn't attached.  Now it simply skips creating the
HNIC.  It might be nice to create the HNIC but not attach it, but it's a
little harder to do that.

This fixes bug 195
Merge pull request #196 from gsilvis/195

Check that HNIC is attached before attaching to bridge