Update and improve crate features in web-sys

* Regenerate the list of features for the crate given recent
  improvements, enabling some more types to be bound.
* Add feature gates for the `css` and `console` namespaces (modules),
  gating the APIs by default. Now `web_sys` has zero APIs unless they're
  requested.
* Improved the "required feature" documentation for `struct` types to
  not list parent classes and mention just the `struct` type instead.

crates/web-sys/build.rs

@@ -69,6 +69,7 @@ fn try_main() -> Result<(), failure::Error> {
     }
 
     // If we're printing all features don't filter anything
+    println!("cargo:rerun-if-env-changed=__WASM_BINDGEN_DUMP_FEATURES");
     let allowed = if env::var("__WASM_BINDGEN_DUMP_FEATURES").is_ok() {
         None
     } else {