[REF] Refactoring according to the first review of CHS

addons/calendar/__init__.py

addons/calendar/__openerp__.py

addons/calendar/calendar_data.xml

addons/calendar/calendar_demo.xml

addons/calendar/calendar_view.xml

addons/calendar/contacts.py

addons/calendar/contacts_view.xml

addons/calendar/controllers/main.py

addons/calendar/models.py

addons/calendar/security/ir.model.access.csv

addons/calendar/static/src/js/base_calendar.js

addons/calendar/static/src/xml/base_calendar.xml

addons/google_calendar/controllers/main.py