Setup JaCoCo

Summary:

• Cleaning the build.gradle
• Remove parallel unit testing (the API doesn't handle them)
• Update the API
• Make Method & Request public (the tests can't find them if they are internal)
• Catch cases in which the JSON returned by the API cannot be parsed, and replace it with dummy JSON
• Integration JaCoCo into the Continuous Integration jobs
• Setting the mandatory coverage ratio to 50% because the current app is only at 60%. WILL NEED to be changed back later.

Closes T328

Test Plan: https://gitlab.com/wildfyre/lib/pipelines/61653442

Reviewers: Info-Screen, WyldBot, Hackintosh5

Reviewed By: WyldBot

Maniphest Tasks: T328

Differential Revision: https://phabricator.wildfyre.net/D252