Migrate to architecture components

[dr0pdb]

Currently the project doesn't follow any architecture. Since the architecture components have been stable for sometime, i think this would be right time to migrate to MVVM architecture.

This can be done by:

• [ ] Creating ViewModel for Activities/Fragments
• [ ] Wrapping Data from Database to LiveData in the ViewModel(Done along with the first step)
• [ ] Migrating to ROOM
• [ ] Writing ViewModel tests

Please create child issues for this and contribute :)