Upgrade JSDoc to 3.3.0-alpha 5

Note: this pull includes the changes from #1743 so merge that first.

This upgrades JSDoc from 3.0 to 3.3.0-alpha5, the latest available version.  This version runs in Node instead of Rhino, and as a result, runs much faster.  

I've build locally and deployed to 

http://cesium.blob.core.windows.net/shunter-jsdoc-upgrade/index.html

so you can easily take a look.

To generate documentation, you must install NodeJS and run `npm install` in the Cesium directory to install JSDoc from npm.  Once this goes in, I'll update the contributor's guide.

Due to our previous heavy hackery of the JSDoc source, I rewrote the template to apply our desired customizations without needing changes to JSDoc.  Along the way, I changed basically everything about the HTML, including formatting changes.  I'm open to revisions.  I based the template on the default, but at this point  we "own" the code in there now, to change as we see fit.

As per @pjcozzi, I dropped support for documenting GLSL.

Fixes  #1687