Move from WebIDL to Node.js-like documentation format

[grgustaf]

PR #1470 was a step in this direction, but only for documenting events. We'd like to move our documentation to be more like Node instead of WebIDL.

[grgustaf]

PR #1747 was another step in this direction for Buffer. However, an external contributor recently mentioned interest in auto-generating code based on the WebIDL and intends to make ours spec-compliant, so we should consider retaining it.