Add dash.js advanced samples

[epiclabsDASH]

New reorganization of dash.js samples. I added a new advanced section and added a couple of samples covering two of the most recurrent questions:

• ABR Custom rules. How to define a custom ABR rule and how to setup it in dash.js.
• Extend mechanism. A sample that shows how to use dash.js extend mechanism to modify requests done by the player (ex: add custom http headers, modify request urls, etc).

Also took advantage of this PR to remove build/typings/index.d.ts. Pointed out by @nicosang, given this is an auto-generated file, doesn't make sense keeping it in development branch.