updated network diagram.

Added a network/environment diagram. Protocols, dependencies and other information is displaced.
Remove ReachableAddresses from app and mon torrc
Remove links to outdated demo instance
Clarify and move instructions for contributors above the fold
Fix broken link and update prereqs in install doc
Move contributors link below technical summary for better top to bottom flow
Cleanup links and formatting for README's "how to" sections
Add acronym for Secure Viewing Station, grammar fixes
Recommend removing unneeded hardware from the SVS, and clarify
Explanation and recommendations for possible choices of transfer device
Better organization of howto sections
Remove "before you begin" from README (should be in install docs)
Try different image link on Github
Merge full_install.md into install.md

Also splits the Google Authenticator instructions into a separate
document.
Add TOC to install document
Correct FPF site URL
Correct FPF domain
Merge pull request #730 from dolanjs/env_diagram

updated network diagram
Build OSSEC agent deb in app-build by default

I had previously asked James to disable building the OSSEC debs in
app-build because it was slowing down my debug cycle. However, I think
in general this is the right thing to do.
Get build_deb_packages.sh working

* Update the path to the fpf-signing-key file, which was moved
  in a refactor.
* Always create the build artifacts directory to avoid an error on first
  run