Add simple_setup_example

[fantavlik]

This is a much simpler example of a Setup Page that doesn't use Backbone nor React nor promisify, simply: SimpleXML, Javascript, and CSS and utilizes the Splunk SDK for Javascript to store a password in storage/passwords and mark the app is_configured=1.

[tacole02]

OMG one JS file.... barely over 100 lines. I am so amazed. I cannot wait to get this into the docs :)