protocol-reference.html: Add option to switch to advanced view

This adds a dropdown field at the top of the page to switch between
"simple" and "advanced" views.

In "simple" view, each control shows only one code example for the
Arduino library. In "advanced" view, detailed information about inputs
and outputs (addresses, masks, etc) is displayed and all code examples are shown.
protocol-reference.html: Clicking a code snippet selects it (for easy copy and paste)
Merge pull request #10 from jboecker/issue9

Fix #9 (more interactivity for protocol-reference.html)