Giant code reorganization (#690)

Code restructure

web/syscalls/client_code_widget.ts

@@ -1,4 +1,4 @@
-import { SysCallMapping } from "../../plugos/system.ts";
+import { SysCallMapping } from "../../lib/plugos/system.ts";
 import { reloadAllMarkdownWidgets } from "../cm_plugins/markdown_widget.ts";
 import { broadcastReload } from "../components/widget_sandbox_iframe.ts";