History is now stored in a lightweight ORM database.
Corners cases are still not treated, but simple calls are saved properly.

Every call is considered has a Conference, holding one or several SipCall.
This simplify extraction and storage of calls in history. It also provide a unique interface
to handle calls instead of two (which were SipCall and Conference).

This commit also fixes minor indent errors and remove unused class
AnimationManager.

We now have a feedback on wifi strength during a call in application log.
Some testing should be done but it seems reliable.
It should be integrated in the user interface in the future.

Issue was caused by retrieving the wrong reference on the displayed screen.

sflphone module

This commit impacts the whole structure app, because we now have
nested Fragments. To keep retro-compatibility, we switched from normal
Fragment to Fragment from the support library.

    - one liner bug in call UI