Summary:
In the network plugin, add features to import and export routes as described in issue https://github.com/facebook/flipper/issues/1651
Primary use case is that external testers (such as QA teams) would be able to create test data, convert it to mocks and save the mocks to make bug fixes easier for devs.
Here is a screenshot showing location of buttons to perform import/export (and clearing) of mock routes:

Here is another screenshot showing export dialog:

Changelog: [Network] Mock routes can now be imported and exported. Thanks bizzguy!
Pull Request resolved: https://github.com/facebook/flipper/pull/1855
Test Plan:
Performed manual testing
- create new mocks
- export mocks
- clear mocks
- import mocks
- verify that mocks still work by making GET/POST requests in sample app
Performed various permutations of above manual tests, including restarting Flipper at various points to ensure that test plan still worked. Also performed visual inspection of exported files to verify correctness.
Would be very interested in learning how to create automated tests for this functionality.
Reviewed By: passy
Differential Revision: D26072928
Pulled By: mweststrate
fbshipit-source-id: 51bd5e19e78d830b94add850d5dc9b9e45fa6fad