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]

request/tests/test-request.js

@@ -10,10 +10,8 @@ o.spec("request", function() {
 	var mock, request, complete
 	o.beforeEach(function() {
 		mock = xhrMock()
-		var requestService = Request(mock, PromisePolyfill)
-		request = requestService.request
 		complete = o.spy()
-		requestService.setCompletionCallback(complete)
+		request = Request(mock, PromisePolyfill, complete).request
 	})
 
 	o.spec("success", function() {
@@ -835,10 +833,7 @@ o.spec("request", function() {
 			// if you use the polyfill, as it's based on `setImmediate` (falling
 			// back to `setTimeout`), and promise microtasks are run at higher
 			// priority than either of those.
-			var requestService = Request(mock, Promise)
-			request = requestService.request
-			complete = o.spy()
-			requestService.setCompletionCallback(complete)
+			request = Request(mock, Promise, complete).request
 			mock.$defineRoutes({
 				"GET /item": function() {
 					return {status: 200, responseText: "[]"}