Massive restructure of plugin API

plug-api/silverbullet-syscall/mod.ts

@@ -0,0 +1,7 @@
+export * as clientStore from "./clientStore.ts";
+export * as editor from "./editor.ts";
+export * as index from "./index.ts";
+export * as markdown from "./markdown.ts";
+export * as sandbox from "./sandbox.ts";
+export * as space from "./space.ts";
+export * as system from "./system.ts";