Road to Kontalk 5.0

Kontalk is starting to become a big project and lately it's been growing a bit uncontrollably. Some refactoring is needed a this stage, before implementing OMEMO, expected for version 5.0. Special care must be taken for:

• modularization of app components, especially for the UI part
• drop usage of intents and broadcasts for message center service communication. Use AIDL or some other sort of IPC
• move the message center to another process
• convert Smack classes into Smack managers
• use DI for UI views (also investigate other uses to simplify code)
• use a database library or build something easier to use without exposing too much low-level stuff
• read contact information directly from system contacts (that is, store only phone:hash associations)
• support for multiple encryption methods
• refactor compose fragments after having modularized everything inside it. Ok for the common parent class, but the father was designed too much "to be for the children"
• unit and automated tests