Deservicify core (#2458)

* De-servicify router (mostly)

Still uses the redraw service, but it no longer has an intermediate
service of its own.

Also, did a *lot* of test deduplication in this. About 30-40% of the
router service tests were already tested on the main router API instance
itself.

Bundle size decreased from 9560 to 9548 bytes min+gzip.

* Merge `m.mount` + `m.redraw`, update router

Simplifies the router and redraw mechanism, and makes it much easier to
keep predictable.

Bundle size down to 9433 bytes min+gzip, docs updated accordingly.

* Make `mithril/render` just return the `m.render` function directly.

* Deservicify `m.render`, revise `m.route`

- You now have to use `mithril/render/render` directly if you want an
  implicit redraw function. (This will likely be going away in v3.)
- Revise `m.route` to only `key` components

* Add `redraw` to `m.render`, deservicify requests

* Test error logging

* Update docs + changelog [skip ci]

docs/index.md

@@ -18,7 +18,7 @@ It's small (< 10kb gzip), fast and provides routing and XHR utilities out of the
 <div style="display:flex;margin:0 0 30px;">
 	<div style="width:50%;">
 		<h5>Download size</h5>
-		<small>Mithril (9.6kb)</small>
+		<small>Mithril (9.4kb)</small>
 		<div style="animation:grow 0.08s;background:#1e5799;height:3px;margin:0 10px 10px 0;transform-origin:0;width:4%;"></div>
 		<small style="color:#aaa;">Vue + Vue-Router + Vuex + fetch (40kb)</small>
 		<div style="animation:grow 0.4s;background:#1e5799;height:3px;margin:0 10px 10px 0;transform-origin:0;width:20%"></div>