Link to CC license pages

* Update license page template
* Add code to ExtendedTrack class to handle each license
* Add links/URLs to track templates
** (Also improve the copyright notice in the JSON API)

The pages provide the actual license terms
(Assume Version 3.0 because that was the latest when support was added)
Use Creative Commons's CC0 tool for public domain
Add missing parenthesis
Merge pull request #20 from jack126guy/licenseupdate

CC license links