Create a Backend class function "live?"

Denotes if interval based updates can be assumed to work. False for flatfiles,
true unless otherwise overloaded
Change gon variable to use metric hash

Change from gon.metric and gon.feed to gon.metrics as an object of multiple
values. Change stacked and standard js files accordingly
Change horizon.js to suit new gon variable format
update .gitignore - ignore all public/flatfile*.csv