Unload uninstalled plugins from Electron cache

Summary: Electron/Node.js does not garbage collects unloaded modules by default. Need to cleanup require.cache to fully unload them.

Reviewed By: passy

Differential Revision: D25545962

fbshipit-source-id: 4dce32f39e22adcd2b4f5a55853551379e786e7b

desktop/types/nodejs.d.ts

@@ -11,7 +11,11 @@ declare module NodeJS {
   interface Global {
     __REVISION__: string | undefined;
     __VERSION__: string;
-    electronRequire: (name: string) => any;
+    electronRequire: {
+      (name: string): any;
+      resolve: (module: string) => string;
+      cache: {[module: string]: any};
+    };
     window: Window | undefined;
     WebSocket: any;
     fetch: any;