Documented API calls' return format.
Fixed some spacing.
Improve API call descriptions

Added more explicit descriptions about API calls that return JSON objects.
Fixed some ambiguous wording.
Fixed some icky spacing.
Fix vncport value in example

Change from string to int.  Change to a realistic value.
Clarified some documentation

Documented the scenarios that the vncport field in show_headnode can be None
Remove old concepts from overview.md
Spruce up haas.cfg.example.

There are now two example configs, one for development, another for
production. The comments in both have been adjusted to be more useful.
Update README, write HACKING.

The README is now less developer-biased; It points to the INSTALL and
HACKING docs as appropriate.

This patch also updates a few things that were out of date, e.g. the
direct use of IPMI by users, and the mac address parameter to the
headnode_create_hnic call in one of the examples.
Address @ryabouza's comments.
Add note about VXLAN to overview.md
README: Fix broken link.

I'd apparently lost the footnote part of the footnote link, but @gsilvis and I
are in agreement that this was kindof gross anyway -- "click here" is not
something one should write in a document that may be read in source form.
I've reworded slightly instead.
Merge pull request #310 from ryabouza/rest-api-calls-doc

Documented API calls' return format.
Merge pull request #351 from gsilvis/overview

Remove old concepts from overview.md
Merge pull request #353 from zenhack/intro-docs-cleanup

Intro docs cleanup