Implement elRepo.io unit testing

ElRepo.io is an Android app that combines the RetroShare JSON API with a Flutter frontend aimed to share content into the RetroShare F2F network. Actually elRepo.io is on a beta state and need a series of feature implementation and unit testing to improve the user experience and scalability of the project. Together with my mentors I expect to implement desired features and unit testing, learning how Flutter works together with a first landing into RetroShare decentralized world.