project: reorganize structure, begin mvvm

This patch reorganizes the project structure to separate entities in
specific groups.
It also renames some files.

This is done to improve the separation of concerns of the components
of the project.
The renaming operation reflects the MVVM architecture that we will try
to implement.

Tuleap: #1327
Change-Id: I46109e82c87510e134f57d551946499b11334c44