[FIX] router: add support for more arbitrary param placements in paths

Before this commit, params in paths had to be be between slashes and
comprise the entirety of the contents between those slashes (eg:
`/books/{{id}}/{{name}}`)

This is unnecessarily restrictive. This commit removes this restriction,
which allows for paths such as:
- `/books/{{id}}-{{name}}`
- `#books&id={{id}}&name={{name}}`

among others

closes #858

tests/router/test_router.ts

@@ -1,4 +1,5 @@
-import { Router } from "../../src/router/router";
+import { Router, Route, RouterEnv } from "../../src/router/router";
+import { makeTestEnv } from "../helpers";
 import { QWeb } from "../../src/qweb/index";
 
 export class TestRouter extends Router {
@@ -13,3 +14,13 @@ export class TestRouter extends Router {
     }
   }
 }
+
+export function getRouteParams(route: Partial<Route>, path: string) {
+  const env = <RouterEnv>makeTestEnv();
+  const router = new TestRouter(env, [route]);
+  const {
+    routeIds: [routeId],
+    routes,
+  } = router;
+  return router["getRouteParams"](routes[routeId], path);
+}