Multi is the default api for methods, it is not necessary to explicitly
decorate methods with it, adds clutter and most people use it because
they see that the rest of the code uses it.
Done with `find . -type f -name '*.py' | xargs sed -i '/@api.multi/d'`
Purpose
=======
An employee and its current contract should have the same
calendar. Currently, if the contract's calendar is changed,
the employee's calendar is not changed.
In the same way, if a contract is created directly in `open`
state, the employee's calendar is not changed.
Finally, the calendar synchronization when the employee
contract is changed is only done in payroll, for no reason.
Specification
=============
Fix the three issues described above.
If the employee's calendar is nonetheless manually changed, a warning
should be displayed if there is a mismatch between both calendars.
Adrian Torres