New Getting Started Content

add new script to pull images from Dockerhub
remove dummy "Getting Started" title from TOC
remove versioning, update TOC
restructure the instructions to prioritize the all-in-one option
address ferris/arnaud comments

this addition removes the outdated sfhackfest getting started material
and replaces it with a refactored version of the end to end
a script nexus-download-dockerimages.sh is used to pull the published
Hyperledger images and then there are three approaches to ultimately
setting up the network: published images, make images, use native binaries
Tested on mac and Linux

preview here - http://fabric-rtd.readthedocs.io/en/latest/getting_started.html
[ci-skip]

Change-Id: I4f8cf910b8458564693a31b754c3486a1e8486ce
Signed-off-by: Nick Gaski <[email protected]>

Author: nickgaski