Refactors signing/verifiying functionality to be part of the Cryptographer

- All encryption/decryption and signing/verifying calls are performed by the cryptographer now.

- The current signature format is temporal. We should define something not base on json.

- Some Cryptographer tests are still missing.

- The cli tests should be modified to fit this too.

test/unit/test_appointment.py

@@ -112,10 +112,11 @@ def test_from_dict(appointment_data):
             assert True
 
 
+# This test is pretty worthless atm, it would make sense once we have a proper serialize function
 def test_serialize(appointment_data):
     appointment = Appointment.from_dict(appointment_data)
 
     assert appointment.triggered is False
     ser_appointment = appointment.serialize()
 
-    assert ser_appointment == json.dumps(appointment_data, sort_keys=True, separators=(",", ":")).encode("utf-8")
+    assert ser_appointment == appointment.to_dict(include_triggered=False)