No More Collab. Fixes #449

* Fully removes real-time collaboration
* URL scheme rewrite

plug-api/silverbullet-syscall/collab.ts

@@ -1,9 +0,0 @@
-import { syscall } from "./syscall.ts";
-
-export function start(serverUrl: string, token: string, username: string) {
-  return syscall("collab.start", serverUrl, token, username);
-}
-
-export function stop() {
-  return syscall("collab.stop");
-}

plug-api/silverbullet-syscall/mod.ts

@@ -3,7 +3,6 @@ export * as index from "./index.ts";
 export * as markdown from "./markdown.ts";
 export * as space from "./space.ts";
 export * as system from "./system.ts";
-export * as collab from "./collab.ts";
 // Legacy redirect, use "store" in $sb/plugos-syscall/mod.ts instead
 export * as clientStore from "./store.ts";
 export * as sync from "./sync.ts";