Make networks more specializable

See docs/networks.md for details
Implement new network_create API

To make the test transition nicer, make a helper function in test_common, that
imitates the old network_create API.
Don't delete projects that can access nodes
Test creation of fancy networks
Fix CLI for network_create
Clean up and document fancy_networks test
Document and improve network_create

- network_create now takes 'admin' instead of '' for admin-created networks
- docs are now cross-referenced with docs/networks.md
- 'ownership' has been clarified
- network_create_simple has been explained better, and turned into a CLI call
  as well.  (It's quite useful for the end-user.)
Fix whitespace errors in fancy-networks code
Merge pull request #275 from gsilvis/fancy-networks

Fancy networks