Clean up Django Rest Framework API URLs and remove auth requirement

DRY API to GET list of Battles, Battle by given {id}, and list of
Players for Battle by given {id}.  Remove authentication /
authorization requirement for user to be Admin user.
Add AngularJS v1.2.23 support + set up hbattleApp app module

Add AngularJS library via Google CDN to base template and set <body>
as root element for new hbattleApp module (assuming template being used
at any time extends base.html), also included/added to the base.html
template.