Serialize Store

Summary:
This diff adds the capability to export the flipper data to a file. With this diff you can click on the "Export Flipper" option from the "Edit" menu in menubar. It will export it in the file at this location

`~/.flipper/MessageLogs.json`

We do not exactly export the store, but just the important part of it. We export in the following format

```
{
fileVersion: '1.0',
device: {
   os: 'iOS',
   title: 'iPhone 7',
   serial: '',
   deviceType: 'physical',
  },
clients: [
   {
    query: {
       app: 'Facebook',
      },
      d: '12345678'
     },
   {
    query: {
       app: 'Instagram',
      },
    id: '12345678'
   }
],
store: {
   pluginState: {},
   notifications: {}
  }
}

```

In next diff I will add the capability to select the folder to export the file too.

Reviewed By: danielbuechele

Differential Revision: D13751963

fbshipit-source-id: 7d3d49c6adf8145b2181d2332c7dbd589155cec3

src/utils/exportData.js

@@ -0,0 +1,76 @@
+/**
+ * Copyright 2018-present Facebook.
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ * @format
+ */
+import fs from 'fs';
+import os from 'os';
+import path from 'path';
+
+const exportFilePath = path.join(
+  os.homedir(),
+  '.flipper',
+  'FlipperExport.json',
+);
+
+export const exportStoreToFile = (data: Store): Promise<void> => {
+  const state = data.getState();
+  const json = {
+    fileVersion: '1.0.0',
+    device: {},
+    clients: [],
+    store: {
+      pluginStates: {},
+      activeNotifications: [],
+    },
+  };
+
+  const device = state.connections.selectedDevice;
+  if (device) {
+    const {serial} = device;
+    json.device = device.toJSON();
+    const clients = state.connections.clients
+      .filter(client => {
+        return client.query.device_id === serial;
+      })
+      .map(client => {
+        return client.toJSON();
+      });
+
+    json.clients = clients;
+
+    const allPluginStates = state.pluginStates;
+    let pluginStates = {};
+    for (let key in allPluginStates) {
+      const filteredClients = clients.filter(client => {
+        let keyArray = key.split('#');
+        keyArray.pop(); // Remove the last entry related to plugin
+        return client.id.includes(keyArray.join('#'));
+      });
+      if (filteredClients.length > 0) {
+        pluginStates = {...pluginStates, [key]: allPluginStates[key]};
+        json.store.pluginStates = pluginStates;
+      }
+    }
+
+    const allActiveNotifications = state.notifications.activeNotifications;
+    let activeNotifications = allActiveNotifications.filter(notif => {
+      const filteredClients = clients.filter(client =>
+        client.id.includes(notif.client),
+      );
+      return filteredClients.length > 0;
+    });
+    json.store.activeNotifications = activeNotifications;
+    return new Promise((resolve, reject) => {
+      fs.writeFile(exportFilePath, JSON.stringify(json), err => {
+        if (err) {
+          reject(err);
+        }
+        resolve();
+      });
+    });
+  }
+  console.error('Make sure a device is connected');
+  return new Promise.reject(new Error('No device is selected'));
+};